Struct Embedding (Composition over Inheritance)

package main

import "fmt"

type Logger struct {
    prefix string
}

func (l *Logger) Log(msg string) {
    fmt.Printf("[%s] %s\n", l.prefix, msg)
}

type Server struct {
    *Logger                       // embedded — promotes Log() onto Server
    addr string
}

func (s *Server) Start() {
    s.Log("starting on " + s.addr)              // calls embedded Logger.Log
}

func main() {
    srv := &Server{
        Logger: &Logger{prefix: "SRV"},
        addr:   ":8080",
    }
    srv.Start()           // [SRV] starting on :8080
    srv.Log("manual")     // [SRV] manual
    // Access the embedded field directly if needed:
    fmt.Println(srv.Logger.prefix)
}