如何知道我们可以在go包中使用的功能？

Question

I am learning the go language and write my first go program, with the help of some web sources:

package main

import (
    "fmt"
    "crypto/sha512"
    "encoding/base64"
)

func main() {

    ba := []byte("HelloWorld")
    hasher := sha512.New()
    hasher.Write(ba)
    sha := base64.StdEncoding.EncodeToString(hasher.Sum(nil))

    fmt.Printf(sha)

}

It compiles and works as expected, but I couldn't write this code myself since if i look at the Go package reference for sha256, I don't see the Write() and the Sum() methods. Where to find this kind of information? Maybe, I'm not reading the good document, or there is a sort of "inheritance" I didn't see.

Answer 1

The hash implementations are all provided through a common hash.Hash interface.

If you look at the docs for sha512.New, you'll see that it returns a hash.Hash, which lists all the Hash specific methods.

The first field in the hash.Hash interface is an embedded io.Writer, which is what provides the standard Write method.

All these values are links in the documentation, which you can follow the to the required definitions, and even to the source.