https://codeeval.dev/gist/202b9b74c1d7070aeef2ee1ed8a66ce5

Notice that in m["key1"] = append(m["key1"], 8) we don't have to check if m["key1"] exists. This is a result of interplay of 3 rules:

• m["foo"] returns zero-value if foo key is not present is the map
• zero-value of slice is nil
• a = append(nil, 3) is valid and creates a single-element slice []int{3}