In encode.go, type encodeState has two methods, stringBytes and string, each of which return (int, error). In both cases, the only error that is returned from the methods is nil, and the int that is returned is never read:

• _, err := e.stringBytes(...) on lines 449, 465
• e.string(...) on lines 544, 546, 580, 615

Return values are similarly ignored in encode_test.go:

• _, err := e.string(...) on line 384
• _, err := e.stringBytes(...) on line 390

I believe these methods can simply return nothing without any change in functionality.