Proper method to hash an arbitrary object

Question

I am writing a data structure that needs to hash an arbitrary object. The following function seems to fail if I give an int is the parameter.

func Hash( obj interface{} ) []byte {
    digest := md5.New()
    if err := binary.Write(digest, binary.LittleEndian, obj); err != nil {
        panic(err)
    }
    return digest.Sum()
}

Calling this on an int results in:

panic: binary.Write: invalid type int

What is the right way to do this?

Answer 1

I found that a good way to do this is to serialize the object using the "gob" package, along the following lines:

var (
    digest = md5.New()
    encoder = gob.NewEncoder(digest)
)

func Hash(obj interface{}) []byte {
    digest.Reset() 
    if err := encoder.Encode(obj); err != nil {
        panic(err)
    }
    return digest.Sum()
}

Edit: This does not work as intended (see below).

Answer 2

binary.Write writes "a fixed-size value or a pointer to a fixed-size value." Type int is not a fixed size value; int is "either 32 or 64 bits." Use a fixed-size value like int32.