add environment support of opentelemetry propagation for package gctx

os/gctx/gctx.go

@@ -9,8 +9,12 @@ package gctx
 
 import (
 	"context"
+	"os"
+	"strings"
 
 	"github.com/gogf/gf/v2/net/gtrace"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
 )
 
 type (
@@ -18,13 +22,36 @@ type (
 	StrKey string            // StrKey is a type for warps basic type string as context key.
 )
 
+var (
+	// processCtx is the context initialized from process environment.
+	processCtx context.Context
+)
+
+func init() {
+	// All environment key-value pairs.
+	m := make(map[string]string)
+	i := 0
+	for _, s := range os.Environ() {
+		i = strings.IndexByte(s, '=')
+		m[s[0:i]] = s[i+1:]
+	}
+	// OpenTelemetry from environments.
+	processCtx = otel.GetTextMapPropagator().Extract(
+		context.Background(),
+		propagation.MapCarrier(m),
+	)
+}
+
 // New creates and returns a context which contains context id.
 func New() context.Context {
-	return WithCtx(context.Background())
+	return WithCtx(processCtx)
 }
 
 // WithCtx creates and returns a context containing context id upon given parent context `ctx`.
 func WithCtx(ctx context.Context) context.Context {
+	if CtxId(ctx) != "" {
+		return ctx
+	}
 	if gtrace.IsUsingDefaultProvider() {
 		var span *gtrace.Span
 		ctx, span = gtrace.NewSpan(ctx, "gctx.WithCtx")