Using impl to create an implementation of the hash interface

impl_hash.go

func (Foo) Write(p []byte) (n int, err error) {
	panic("not implemented") // TODO: Implement
}

// Sum appends the current hash to b and returns the resulting slice.
// It does not change the underlying hash state.
func (Foo) Sum(b []byte) []byte {
	panic("not implemented") // TODO: Implement
}

// Reset resets the Hash to its initial state.
func (Foo) Reset() {
	panic("not implemented") // TODO: Implement
}

// Size returns the number of bytes Sum will return.
func (Foo) Size() int {
	panic("not implemented") // TODO: Implement
}

// BlockSize returns the hash's underlying block size.
// The Write method must be able to accept any amount
// of data, but it may operate more efficiently if all writes
// are a multiple of the block size.
func (Foo) BlockSize() int {
	panic("not implemented") // TODO: Implement
}