Исходники и презентации

lessons/contexts/context_with_value/main.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"context"
+	"fmt"
+)
+
+func main() {
+	traceCtx := context.WithValue(context.Background(), "trace_id", "12-21-33")
+	makeRequest(traceCtx)
+
+	oldValue, ok := traceCtx.Value("trace_id").(string)
+	if ok {
+		fmt.Println("mainValue", oldValue)
+	}
+}
+
+func makeRequest(ctx context.Context) {
+	oldValue, ok := ctx.Value("trace_id").(string)
+	if ok {
+		fmt.Println("oldValue", oldValue)
+	}
+
+	newCtx := context.WithValue(ctx, "trace_id", "22-22-22")
+	newValue, ok := newCtx.Value("trace_id").(string)
+	if ok {
+		fmt.Println("newValue", newValue)
+	}
+}