To base64-decode a string in Go, you can use the decoding.DecodeString function from the encoding/base64 package. This function takes a base64-encoded string as input and returns the decoded data as a byte slice. 

Here’s an example:

package main

import (
	"encoding/base64"
	"fmt"
)

func main() {
	// The string to be decoded:
	encoded := "SGVsbG8gV29ybGQh"

	// Decode the string:
	decoded, err := base64.StdEncoding.DecodeString(encoded)

	if err != nil {
		fmt.Println("Error while decoding the string", 
			err.Error())
	}

	// Print the decoded data:
	fmt.Println(string(decoded))
	// Output: Hello World!

	// Encode it back:
	enc := base64.StdEncoding.EncodeToString(decoded)

	// Output: SGVsbG8gV29ybGQh
	fmt.Println("encoded", enc)
}

That was your nugget 😄.

Until the next one… May the source be with you 🦄.