Merge pull request #18 from unistack-org/flow

flow: initial tests

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
     - name: setup
       uses: actions/setup-go@v2
       with:
-        go-version: 1.15
+        go-version: 1.16
     - name: cache
       uses: actions/cache@v2
       with:

.github/workflows/pr.yml

@@ -11,7 +11,7 @@ jobs:
     - name: setup
       uses: actions/setup-go@v2
       with:
-        go-version: 1.15
+        go-version: 1.16
     - name: cache
       uses: actions/cache@v2
       with:

broker/memory.go

@@ -3,14 +3,13 @@ package broker
 import (
 	"context"
 	"errors"
-	"math/rand"
 	"sync"
-	"time"
 
 	"github.com/google/uuid"
 	"github.com/unistack-org/micro/v3/logger"
 	maddr "github.com/unistack-org/micro/v3/util/addr"
 	mnet "github.com/unistack-org/micro/v3/util/net"
+	"github.com/unistack-org/micro/v3/util/rand"
 )
 
 type memoryBroker struct {
@@ -59,7 +58,8 @@ func (m *memoryBroker) Connect(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	i := rand.Intn(20000)
+	var rng rand.Rand
+	i := rng.Intn(20000)
 	// set addr with port
 	addr = mnet.HostPort(addr, 10000+i)
 
@@ -237,8 +237,6 @@ func (m *memorySubscriber) Unsubscribe(ctx context.Context) error {
 
 // NewBroker return new memory broker
 func NewBroker(opts ...Option) Broker {
-	rand.Seed(time.Now().UnixNano())
-
 	return &memoryBroker{
 		opts:        NewOptions(opts...),
 		Subscribers: make(map[string][]*memorySubscriber),

codec/noop.go

@@ -3,7 +3,6 @@ package codec
 import (
 	"encoding/json"
 	"io"
-	"io/ioutil"
 )
 
 type noopCodec struct {
@@ -20,7 +19,7 @@ func (c *noopCodec) ReadHeader(conn io.Reader, m *Message, t MessageType) error
 
 func (c *noopCodec) ReadBody(conn io.Reader, b interface{}) error {
 	// read bytes
-	buf, err := ioutil.ReadAll(conn)
+	buf, err := io.ReadAll(conn)
 	if err != nil {
 		return err
 	}

flow/dag.go

@@ -0,0 +1,21 @@
+package flow
+
+type node struct {
+	name string
+}
+
+func (n *node) ID() string {
+	return n.name
+}
+
+func (n *node) Name() string {
+	return n.name
+}
+
+func (n *node) String() string {
+	return n.name
+}
+
+func (n *node) Hashcode() interface{} {
+	return n.name
+}

flow/dag_test.go

@@ -0,0 +1,68 @@
+package flow
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/silas/dag"
+)
+
+func checkErr(t *testing.T, err error) {
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestDag(t *testing.T) {
+	d1 := &dag.AcyclicGraph{}
+	d2 := &dag.AcyclicGraph{}
+	d2v1 := d2.Add(&node{"Substep.Create"})
+	v1 := d1.Add(&node{"AccountService.Create"})
+	v2 := d1.Add(&node{"AuthzService.Create"})
+	v3 := d1.Add(&node{"AuthnService.Create"})
+	v4 := d1.Add(&node{"ProjectService.Create"})
+	v5 := d1.Add(&node{"ContactService.Create"})
+	v6 := d1.Add(&node{"NetworkService.Create"})
+	v7 := d1.Add(&node{"MailerService.Create"})
+	v8 := d1.Add(&node{"NestedService.Create"})
+	v9 := d1.Add(d2v1)
+	d1.Connect(dag.BasicEdge(v1, v2))
+	d1.Connect(dag.BasicEdge(v1, v3))
+	d1.Connect(dag.BasicEdge(v1, v4))
+	d1.Connect(dag.BasicEdge(v1, v5))
+	d1.Connect(dag.BasicEdge(v1, v6))
+	d1.Connect(dag.BasicEdge(v1, v7))
+	d1.Connect(dag.BasicEdge(v7, v8))
+	d1.Connect(dag.BasicEdge(v8, v9))
+
+	if err := d1.Validate(); err != nil {
+		t.Fatal(err)
+	}
+
+	d1.TransitiveReduction()
+
+	var steps [][]string
+	fn := func(n dag.Vertex, idx int) error {
+		if idx == 0 {
+			steps = make([][]string, 1, 1)
+			steps[0] = make([]string, 0, 1)
+		} else if idx >= len(steps) {
+			tsteps := make([][]string, idx+1, idx+1)
+			copy(tsteps, steps)
+			steps = tsteps
+			steps[idx] = make([]string, 0, 1)
+		}
+		steps[idx] = append(steps[idx], fmt.Sprintf("%s", n))
+		return nil
+	}
+
+	start := &node{"AccountService.Create"}
+	err := d1.SortedDepthFirstWalk([]dag.Vertex{start}, fn)
+	checkErr(t, err)
+	if len(steps) != 4 {
+		t.Fatalf("invalid steps: %#+v", steps)
+	}
+	if steps[3][0] != "Substep.Create" {
+		t.Fatalf("invalid last step: %#+v", steps)
+	}
+}

flow/flow.go

@@ -0,0 +1,7 @@
+// Package flow is an interface used for saga pattern messaging
+package flow
+
+type Step interface {
+	// Endpoint returns service_name.service_method
+	Endpoint() string
+}

go.mod

@@ -1,15 +1,17 @@
 module github.com/unistack-org/micro/v3
 
-go 1.14
+go 1.16
 
 require (
 	github.com/dgrijalva/jwt-go v3.2.0+incompatible
 	github.com/ef-ds/deque v1.0.4
 	github.com/google/uuid v1.2.0
+	github.com/heimdalr/dag v1.0.1 // indirect
 	github.com/imdario/mergo v0.3.11
 	github.com/kr/text v0.2.0 // indirect
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/patrickmn/go-cache v2.1.0+incompatible
+	github.com/silas/dag v0.0.0-20210121180416-41cf55125c34 // indirect
 	golang.org/x/net v0.0.0-20210119194325-5f4716e94777
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 )

go.sum

@@ -3,8 +3,13 @@ github.com/dgrijalva/jwt-go v3.2.0+incompatible h1:7qlOGliEKZXTDg6OTjfoBKDXWrumC
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/ef-ds/deque v1.0.4 h1:iFAZNmveMT9WERAkqLJ+oaABF9AcVQ5AjXem/hroniI=
 github.com/ef-ds/deque v1.0.4/go.mod h1:gXDnTC3yqvBcHbq2lcExjtAcVrOnJCbMcZXmuj8Z4tg=
+github.com/go-test/deep v1.0.7 h1:/VSMRlnY/JSyqxQUzQLKVMAskpY/NZKFA5j2P+0pP2M=
+github.com/go-test/deep v1.0.7/go.mod h1:QV8Hv/iy04NyLBxAdO9njL0iVPN1S4d/A3NVv1V36o8=
+github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/uuid v1.2.0 h1:qJYtXnJRWmpe7m/3XlyhrsLrEURqHRM2kxzoxXqyUDs=
 github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/heimdalr/dag v1.0.1 h1:iR2K3DSUFDYx0GeV7iXBnZkedWS1xePSGrylQ197uxg=
+github.com/heimdalr/dag v1.0.1/go.mod h1:t+ZkR+sjKL4xhlE1B9rwpvwfo+x+2R0363efS+Oghns=
 github.com/imdario/mergo v0.3.11 h1:3tnifQM4i+fbajXKBHXWEH+KvNHqojZ778UH75j3bGA=
 github.com/imdario/mergo v0.3.11/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
@@ -15,13 +20,12 @@ github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e h1:fD57ERR4JtEqsWb
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
 github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
-github.com/unistack-org/micro v1.18.0 h1:EbFiII0bKV0Xcua7o6J30MFmm4/g0Hv3ECOKzsUBihU=
+github.com/silas/dag v0.0.0-20210121180416-41cf55125c34 h1:vBfVmA5mZhsQa2jr1FOL9nfA37N/jnbBmi5XUfviVTI=
+github.com/silas/dag v0.0.0-20210121180416-41cf55125c34/go.mod h1:7RTUFBdIRC9nZ7/3RyRNH1bdqIShrDejd1YbLwgPS+I=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777 h1:003p0dJM77cxMSyCPFphvZf/Y5/NXf5fzg6ufd1/Oew=
 golang.org/x/net v0.0.0-20210119194325-5f4716e94777/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

network/transport/memory.go

@@ -4,13 +4,13 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"math/rand"
 	"net"
 	"sync"
 	"time"
 
 	maddr "github.com/unistack-org/micro/v3/util/addr"
 	mnet "github.com/unistack-org/micro/v3/util/net"
+	"github.com/unistack-org/micro/v3/util/rand"
 )
 
 type memorySocket struct {
@@ -207,7 +207,8 @@ func (m *memoryTransport) Listen(ctx context.Context, addr string, opts ...Liste
 
 	// if zero port then randomly assign one
 	if len(port) > 0 && port == "0" {
-		i := rand.Intn(20000)
+		var rng rand.Rand
+		i := rng.Intn(20000)
 		port = fmt.Sprintf("%d", 10000+i)
 	}
 
@@ -255,8 +256,6 @@ func (m *memoryTransport) Name() string {
 func NewTransport(opts ...Option) Transport {
 	options := NewOptions(opts...)
 
-	rand.Seed(time.Now().UnixNano())
-
 	return &memoryTransport{
 		opts:      options,
 		listeners: make(map[string]*memoryListener),

resolver/http/http.go

@@ -4,7 +4,7 @@ package http
 import (
 	"encoding/json"
 	"errors"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 
@@ -61,7 +61,7 @@ func (r *HTTPResolver) Resolve(name string) ([]*resolver.Record, error) {
 	if rsp.StatusCode != 200 {
 		return nil, errors.New("non 200 response")
 	}
-	b, err := ioutil.ReadAll(rsp.Body)
+	b, err := io.ReadAll(rsp.Body)
 	if err != nil {
 		return nil, err
 	}

selector/random/random.go

@@ -1,9 +1,8 @@
 package random
 
 import (
-	"math/rand"
-
 	"github.com/unistack-org/micro/v3/selector"
+	"github.com/unistack-org/micro/v3/util/rand"
 )
 
 type random struct{}
@@ -20,10 +19,9 @@ func (r *random) Select(routes []string, opts ...selector.SelectOption) (selecto
 		if len(routes) == 1 {
 			return routes[0]
 		}
-
+		var rng rand.Rand
 		// select a random route from the slice
-		//nolint:gosec
-		return routes[rand.Intn(len(routes))]
+		return routes[rng.Intn(len(routes))]
 	}, nil
 }
 

selector/roundrobin/roundrobin.go

@@ -1,9 +1,8 @@
 package roundrobin
 
 import (
-	"math/rand"
-
 	"github.com/unistack-org/micro/v3/selector"
+	"github.com/unistack-org/micro/v3/util/rand"
 )
 
 // NewSelector returns an initialised round robin selector
@@ -18,8 +17,8 @@ func (r *roundrobin) Select(routes []string, opts ...selector.SelectOption) (sel
 	if len(routes) == 0 {
 		return nil, selector.ErrNoneAvailable
 	}
-
-	i := rand.Intn(len(routes))
+	var rng rand.Rand
+	i := rng.Intn(len(routes))
 
 	return func() string {
 		route := routes[i%len(routes)]

util/http/http_test.go

@@ -3,7 +3,6 @@
 package http
 
 import (
-	"io/ioutil"
 	"net"
 	"net/http"
 	"testing"
@@ -52,7 +51,7 @@ func TestRoundTripper(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	b, err := ioutil.ReadAll(w.Body)
+	b, err := io.ReadAll(w.Body)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -72,7 +71,7 @@ func TestRoundTripper(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	b, err = ioutil.ReadAll(rsp.Body)
+	b, err = io.ReadAll(rsp.Body)
 	if err != nil {
 		t.Fatal(err)
 	}

util/jitter/jitter.go

@@ -2,16 +2,14 @@
 package jitter
 
 import (
-	"math/rand"
 	"time"
-)
 
-var (
-	r = rand.New(rand.NewSource(time.Now().UnixNano()))
+	"github.com/unistack-org/micro/v3/util/rand"
 )
 
 // Do returns a random time to jitter with max cap specified
 func Do(d time.Duration) time.Duration {
-	v := r.Float64() * float64(d.Nanoseconds())
+	var rng rand.Rand
+	v := rng.Float64() * float64(d.Nanoseconds())
 	return time.Duration(v)
 }

util/rand/rand.go

@@ -0,0 +1,84 @@
+package rand
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+)
+
+// Rand is a wrapper around crypto/rand that adds some convenience functions known from math/rand.
+type Rand struct {
+	buf [8]byte
+}
+
+func (r *Rand) Int31() int32 {
+	rand.Read(r.buf[:4])
+	return int32(binary.BigEndian.Uint32(r.buf[:4]) & ^uint32(1<<31))
+}
+
+func (r *Rand) Int() int {
+	u := uint(r.Int63())
+	return int(u << 1 >> 1) // clear sign bit if int == int32
+}
+
+func (r *Rand) Float64() float64 {
+again:
+	f := float64(r.Int63()) / (1 << 63)
+	if f == 1 {
+		goto again // resample; this branch is taken O(never)
+	}
+	return f
+}
+
+func (r *Rand) Float32() float32 {
+again:
+	f := float32(r.Float64())
+	if f == 1 {
+		goto again // resample; this branch is taken O(very rarely)
+	}
+	return f
+}
+
+func (r *Rand) Uint32() uint32 {
+	return uint32(r.Int63() >> 31)
+}
+
+func (r *Rand) Uint64() uint64 {
+	return uint64(r.Int63())>>31 | uint64(r.Int63())<<32
+}
+
+func (r *Rand) Intn(n int) int {
+	if n <= 1<<31-1 {
+		return int(r.Int31n(int32(n)))
+	}
+	return int(r.Int63n(int64(n)))
+}
+
+func (r *Rand) Int63() int64 {
+	rand.Read(r.buf[:])
+	return int64(binary.BigEndian.Uint64(r.buf[:]) & ^uint64(1<<63))
+}
+
+// copied from the standard library math/rand implementation of Int63n
+func (r *Rand) Int31n(n int32) int32 {
+	if n&(n-1) == 0 { // n is power of two, can mask
+		return r.Int31() & (n - 1)
+	}
+	max := int32((1 << 31) - 1 - (1<<31)%uint32(n))
+	v := r.Int31()
+	for v > max {
+		v = r.Int31()
+	}
+	return v % n
+}
+
+func (r *Rand) Int63n(n int64) int64 {
+	if n&(n-1) == 0 { // n is power of two, can mask
+		return r.Int63() & (n - 1)
+	}
+	max := int64((1 << 63) - 1 - (1<<63)%uint64(n))
+	v := r.Int63()
+	for v > max {
+		v = r.Int63()
+	}
+	return v % n
+}

util/reflect/path.go

@@ -0,0 +1,257 @@
+package reflect
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+const (
+	SplitToken     = "."
+	IndexCloseChar = "]"
+	IndexOpenChar  = "["
+)
+
+var (
+	ErrMalformedIndex    = errors.New("Malformed index key")
+	ErrInvalidIndexUsage = errors.New("Invalid index key usage")
+	ErrKeyNotFound       = errors.New("Unable to find the key")
+	ErrBadJSONPath       = errors.New("Bad path: must start with $ and have more then 2 chars")
+)
+
+func Lookup(i interface{}, path string) (reflect.Value, error) {
+	if path == "" || path[0:1] != "$" {
+		return reflect.Value{}, ErrBadJSONPath
+	}
+
+	if path == "$" {
+		return reflect.ValueOf(i), nil
+	}
+
+	if len(path) < 2 {
+		return reflect.Value{}, ErrBadJSONPath
+	}
+
+	return lookup(i, strings.Split(path[2:], SplitToken)...)
+}
+
+// Lookup performs a lookup into a value, using a path of keys. The key should
+// match with a Field or a MapIndex. For slice you can use the syntax key[index]
+// to access a specific index. If one key owns to a slice and an index is not
+// specificied the rest of the path will be apllied to evaley value of the
+// slice, and the value will be merged into a slice.
+func lookup(i interface{}, path ...string) (reflect.Value, error) {
+	value := reflect.ValueOf(i)
+	var parent reflect.Value
+	var err error
+
+	for i, part := range path {
+		parent = value
+
+		value, err = getValueByName(value, part)
+		if err == nil {
+			continue
+		}
+
+		if !isAggregable(parent) {
+			break
+		}
+
+		value, err = aggreateAggregableValue(parent, path[i:])
+
+		break
+	}
+
+	return value, err
+}
+
+func getValueByName(v reflect.Value, key string) (reflect.Value, error) {
+	var value reflect.Value
+	var index int
+	var err error
+
+	key, index, err = parseIndex(key)
+	if err != nil {
+		return value, err
+	}
+	switch v.Kind() {
+	case reflect.Ptr, reflect.Interface:
+		return getValueByName(v.Elem(), key)
+	case reflect.Struct:
+		value = v.FieldByName(key)
+	case reflect.Map:
+		kValue := reflect.Indirect(reflect.New(v.Type().Key()))
+		kValue.SetString(key)
+		value = v.MapIndex(kValue)
+	}
+
+	if !value.IsValid() {
+		return reflect.Value{}, ErrKeyNotFound
+	}
+
+	if index != -1 {
+		if value.Type().Kind() != reflect.Slice {
+			return reflect.Value{}, ErrInvalidIndexUsage
+		}
+
+		value = value.Index(index)
+	}
+
+	if value.Kind() == reflect.Ptr || value.Kind() == reflect.Interface {
+		value = value.Elem()
+	}
+
+	return value, nil
+}
+
+func aggreateAggregableValue(v reflect.Value, path []string) (reflect.Value, error) {
+	values := make([]reflect.Value, 0)
+
+	l := v.Len()
+	if l == 0 {
+		ty, ok := lookupType(v.Type(), path...)
+		if !ok {
+			return reflect.Value{}, ErrKeyNotFound
+		}
+		return reflect.MakeSlice(reflect.SliceOf(ty), 0, 0), nil
+	}
+
+	switch v.Kind() {
+	case reflect.Slice, reflect.Map:
+		break
+	default:
+		return reflect.Value{}, fmt.Errorf("unsuported kind for index")
+	}
+
+	index := indexFunction(v)
+	for i := 0; i < l; i++ {
+		value, err := lookup(index(i).Interface(), path...)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+
+		values = append(values, value)
+	}
+
+	return mergeValue(values), nil
+}
+
+func indexFunction(v reflect.Value) func(i int) reflect.Value {
+	switch v.Kind() {
+	case reflect.Slice:
+		return v.Index
+	case reflect.Map:
+		keys := v.MapKeys()
+		return func(i int) reflect.Value {
+			return v.MapIndex(keys[i])
+		}
+	}
+	return func(i int) reflect.Value { return reflect.Value{} }
+}
+
+func mergeValue(values []reflect.Value) reflect.Value {
+	values = removeZeroValues(values)
+	l := len(values)
+	if l == 0 {
+		return reflect.Value{}
+	}
+
+	sample := values[0]
+	mergeable := isMergeable(sample)
+
+	t := sample.Type()
+	if mergeable {
+		t = t.Elem()
+	}
+
+	value := reflect.MakeSlice(reflect.SliceOf(t), 0, 0)
+	for i := 0; i < l; i++ {
+		if !values[i].IsValid() {
+			continue
+		}
+
+		if mergeable {
+			value = reflect.AppendSlice(value, values[i])
+		} else {
+			value = reflect.Append(value, values[i])
+		}
+	}
+
+	return value
+}
+
+func removeZeroValues(values []reflect.Value) []reflect.Value {
+	l := len(values)
+
+	var v []reflect.Value
+	for i := 0; i < l; i++ {
+		if values[i].IsValid() {
+			v = append(v, values[i])
+		}
+	}
+
+	return v
+}
+
+func isAggregable(v reflect.Value) bool {
+	k := v.Kind()
+
+	return k == reflect.Map || k == reflect.Slice
+}
+
+func isMergeable(v reflect.Value) bool {
+	k := v.Kind()
+	return k == reflect.Map || k == reflect.Slice
+}
+
+func hasIndex(s string) bool {
+	return strings.Contains(s, IndexOpenChar)
+}
+
+func parseIndex(s string) (string, int, error) {
+	start := strings.Index(s, IndexOpenChar)
+	end := strings.Index(s, IndexCloseChar)
+
+	if start == -1 && end == -1 {
+		return s, -1, nil
+	}
+
+	if (start != -1 && end == -1) || (start == -1 && end != -1) {
+		return "", -1, ErrMalformedIndex
+	}
+
+	index, err := strconv.Atoi(s[start+1 : end])
+	if err != nil {
+		return "", -1, ErrMalformedIndex
+	}
+
+	return s[:start], index, nil
+}
+
+func lookupType(ty reflect.Type, path ...string) (reflect.Type, bool) {
+	if len(path) == 0 {
+		return ty, true
+	}
+
+	switch ty.Kind() {
+	case reflect.Slice, reflect.Array, reflect.Map:
+		if hasIndex(path[0]) {
+			return lookupType(ty.Elem(), path[1:]...)
+		}
+		// Aggregate.
+		return lookupType(ty.Elem(), path...)
+	case reflect.Ptr:
+		return lookupType(ty.Elem(), path...)
+	case reflect.Interface:
+		// We can't know from here without a value. Let's just return this type.
+		return ty, true
+	case reflect.Struct:
+		f, ok := ty.FieldByName(path[0])
+		if ok {
+			return lookupType(f.Type, path[1:]...)
+		}
+	}
+	return nil, false
+}

util/reflect/path_test.go

@@ -0,0 +1,34 @@
+package reflect
+
+import (
+	"testing"
+)
+
+func TestPath(t *testing.T) {
+
+	type Nested2 struct {
+		Name string
+	}
+	type Nested1 struct {
+		Nested2 Nested2
+	}
+	type Config struct {
+		Nested1 Nested1
+	}
+
+	cfg := &Config{
+		Nested1: Nested1{
+			Nested2: Nested2{
+				Name: "NAME",
+			},
+		},
+	}
+
+	v, err := Lookup(cfg, "$.Nested1.Nested2.Name")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v.String() != "NAME" {
+		t.Fatalf("lookup returns invalid value: %v", v)
+	}
+}

util/token/jwt/jwt_test.go

@@ -1,7 +1,7 @@
 package jwt
 
 import (
-	"io/ioutil"
+	"os"
 	"testing"
 	"time"
 
@@ -10,7 +10,7 @@ import (
 )
 
 func TestGenerate(t *testing.T) {
-	privKey, err := ioutil.ReadFile("test/sample_key")
+	privKey, err := os.ReadFile("test/sample_key")
 	if err != nil {
 		t.Fatalf("Unable to read private key: %v", err)
 	}
@@ -26,11 +26,11 @@ func TestGenerate(t *testing.T) {
 }
 
 func TestInspect(t *testing.T) {
-	pubKey, err := ioutil.ReadFile("test/sample_key.pub")
+	pubKey, err := os.ReadFile("test/sample_key.pub")
 	if err != nil {
 		t.Fatalf("Unable to read public key: %v", err)
 	}
-	privKey, err := ioutil.ReadFile("test/sample_key")
+	privKey, err := os.ReadFile("test/sample_key")
 	if err != nil {
 		t.Fatalf("Unable to read private key: %v", err)
 	}