A special base64 implementation in Go/Golang (like in Drupal's PhpassHashedPassword::base64Encode())

Question

I have tried to implement a Drupal compatible authentication in Go and use this package for base64 encoding: golang.org/src/encoding/base64/base64.go

The Result: the created and in Drupal saved hashes don't matches. Only after reimplementing Go's base64-package, where I do the bit shifting like in Drupals base64Encode() the hashes matched:

input bit location:                 abcdefgh ijklmnop qrstuvwx
Go's base64.go bit location:        ..abcdef ..ghijkl ..mnopqr ..stuvwx
PHP's base64Encode() bit location:  ..cdefgh ..mnopab ..wxijkl ..qrstuv

Well, I do instead of Google's implementation:

...

for si < n {
            // Convert 3x 8bit source bytes into 4 bytes
            val := uint(src[si+0])<<16 | uint(src[si+1])<<8 | uint(src[si+2])

            dst[di+0] = enc.encode[val>>18&0x3F]
            dst[di+1] = enc.encode[val>>12&0x3F]
            dst[di+2] = enc.encode[val>>6&0x3F]
            dst[di+3] = enc.encode[val&0x3F]

            si += 3
            di += 4
        }

...

my own implementation now with behalf of Drupal's base64Encode()

...

for si < n {
        // Convert 3x 8bit source bytes into 4 bytes
        // val := uint(src[si+0])<<16 | uint(src[si+1])<<8 | uint(src[si+2])
        val := uint(src[si+0]) | uint(src[si+1])<<8 | uint(src[si+2])<<16

        dst[di+0] = enc.encode[val&0x3F] 
        dst[di+1] = enc.encode[val>>6&0x3F]
        dst[di+2] = enc.encode[val>>12&0x3F]
        dst[di+3] = enc.encode[val>>18&0x3F]

        si += 3
        di += 4
    }

...

My Questions:

• is already there in Go an implementation like I did (reimplemented Drupal's base64Encode())?
• does this special base64 encoding have a name? Are there Literature/Publication references?