A type implements an interface by implementing the methods.

There is no explicit declaration of intent.

Implicit interfaces decouple implementation packages from the packages that define the interfaces: neither depends on the other.

It also encourages the definition of precise interfaces, because you don‘t have to find every implementation and tag it with the new interface name.

Package io defines Reader and Writer; you don‘t have to.

package mainimport (    "fmt"    "os")type Reader interface {    Read(b []byte) (n int, err error)}type Writer interface {    Write(b []byte) (n int,err error)}type ReadWriter interface {    Reader    Writer}func main() {    var w Writer        //os.Stdout implements Writer    w = os.Stdout    fmt.Fprintf(w, "hello, writer\n")}

A Tour of Go Interfaces are satisfied implicitly