better.go

// Package better is a better implementation of log.Logger
package better

type Logger struct {
}

func (l *Logger) Print(v ...interface{}) {
   //....
}

// other methods

yourCode.go

package main

import (
  "better"
  "log"
)

// Logger is a subset of log.Logger methods that we need.
type MyLogger interface {
  Print(v ...interface{})
}

func do(l MyLogger) {
  l.Print("doing...")
}

func main() {
  do(log.New(os.Stdout, "", 0))
  do(&better.Logger{})
}