Implement config singleton (#1268)

* Implement config singleton

* Pass token in grpc request headers

* Refactor BearerScheme

* Fix typo

util/config/config.go

@@ -9,39 +9,20 @@ import (
 
 	conf "github.com/micro/go-micro/v2/config"
 	"github.com/micro/go-micro/v2/config/source/file"
+	"github.com/micro/go-micro/v2/util/log"
 )
 
 // FileName for global micro config
 const FileName = ".micro"
 
+// config is a singleton which is required to ensure
+// each function call doesn't load the .micro file
+// from disk
+var config = newConfig()
+
 // Get a value from the .micro file
 func Get(key string) (string, error) {
-	// get the filepath
-	fp, err := filePath()
-	if err != nil {
-		return "", err
-	}
-
-	// create a new config
-	c, err := conf.NewConfig(
-		conf.WithSource(
-			file.NewSource(
-				file.WithPath(fp),
-			),
-		),
-	)
-	if err != nil {
-		return "", err
-	}
-
-	// load the config
-	if err := c.Load(); err != nil {
-		return "", err
-	}
-
-	// set a value
-	tk := c.Get(key).String("")
-
+	tk := config.Get(key).String("")
 	return strings.TrimSpace(tk), nil
 }
 
@@ -53,11 +34,36 @@ func Set(key, value string) error {
 		return err
 	}
 
+	// set the value
+	config.Set(value, key)
+
+	// write to the file
+	return ioutil.WriteFile(fp, config.Bytes(), 0644)
+}
+
+func filePath() (string, error) {
+	usr, err := user.Current()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(usr.HomeDir, FileName), nil
+}
+
+// newConfig returns a loaded config
+func newConfig() conf.Config {
+	// get the filepath
+	fp, err := filePath()
+	if err != nil {
+		log.Error(err)
+		return conf.DefaultConfig
+	}
+
 	// write the file if it does not exist
 	if _, err := os.Stat(fp); os.IsNotExist(err) {
 		ioutil.WriteFile(fp, []byte{}, 0644)
 	} else if err != nil {
-		return err
+		log.Error(err)
+		return conf.DefaultConfig
 	}
 
 	// create a new config
@@ -69,25 +75,16 @@ func Set(key, value string) error {
 		),
 	)
 	if err != nil {
-		return err
+		log.Error(err)
+		return conf.DefaultConfig
 	}
 
 	// load the config
 	if err := c.Load(); err != nil {
-		return err
+		log.Error(err)
+		return conf.DefaultConfig
 	}
 
-	// set a value
-	c.Set(value, key)
-
-	// write the file
-	return ioutil.WriteFile(fp, c.Bytes(), 0644)
-}
-
-func filePath() (string, error) {
-	usr, err := user.Current()
-	if err != nil {
-		return "", err
-	}
-	return filepath.Join(usr.HomeDir, FileName), nil
+	// return the conf
+	return c
 }