如何仅用4位来表示Go中的数字？

I am trying to compress the representation of a number into fewer bits. For example, right now I am using a float64 to represent a number such as 8.0. I only need 4 bits to represent 8.0, so I was trying to find a way to convert the float64 representation into a 4 bit representation. I know I can use an uint8 to represent 8 using only 8 bits, but that is not enough for my application. I need to squeeze those little extra bits in space.

I looked around the Go standard library, but did not find anything that would allow me to represent a number in less than 8 bits. Did I miss a package that can help me do this? How can I approach this problem?

The Go standard library does have an example of variable-length numbers.

package main

import (
    "encoding/binary"
    "fmt"
)

func main() {
    buf := make([]byte, binary.MaxVarintLen64)
    x := int64(8)
    n := binary.PutVarint(buf[:cap(buf)], x)
    buf = buf[:n]
    fmt.Println(x, len(buf), buf)
    y, m := binary.Varint(buf)
    fmt.Println(y, m)
}

Playground: https://play.golang.org/p/-p6M6OSHcMF

Output:

8 1 [16]
8 1