On lastest master commit, in encoding/json/decode.go file, there are two variations of spelling of the same word:

var spellingOccurrences = map[string]int{
    "unmarshaling":  2,
    "unmarshalling": 1,
}

It can be made better by having a consistent spelling, making it easier to find out which is the canonical spelling.

Edit: Including test files and "marshaling"/"marshalling", the count goes to 8 and 3, respectively.