add config

config/source/env/options.go

@@ -0,0 +1,49 @@
+package env
+
+import (
+	"context"
+
+	"strings"
+
+	"github.com/micro/go-micro/config/source"
+)
+
+type strippedPrefixKey struct{}
+type prefixKey struct{}
+
+// WithStrippedPrefix sets the environment variable prefixes to scope to.
+// These prefixes will be removed from the actual config entries.
+func WithStrippedPrefix(p ...string) source.Option {
+	return func(o *source.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+
+		o.Context = context.WithValue(o.Context, strippedPrefixKey{}, appendUnderscore(p))
+	}
+}
+
+// WithPrefix sets the environment variable prefixes to scope to.
+// These prefixes will not be removed. Each prefix will be considered a top level config entry.
+func WithPrefix(p ...string) source.Option {
+	return func(o *source.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, prefixKey{}, appendUnderscore(p))
+	}
+}
+
+func appendUnderscore(prefixes []string) []string {
+	var result []string
+	for _, p := range prefixes {
+		if !strings.HasSuffix(p, "_") {
+			result = append(result, p+"_")
+			continue
+		}
+
+		result = append(result, p)
+	}
+
+	return result
+}