Go — Maps (basics)

Go’s version of other languages’ Hash and Dict are called Maps.

To create a Map, you can use the make function. Here, we create a map with keys of type string and values of type int:

m := make(map[string]int)
m["k1"] = 7
m["k2"] = 13

To access a value in the map, use the square bracket notation as shown above (m["k1"] = 7). You can also initialize a map and assign values in a single line:

m := map[string]int{"bar": 7, "baz": 11}

The built-in function len returns the number of key/value pairs in a map:

fmt.Println("len:", len(m)) // 2

To delete a key/value pair from the map, use the delete function. Here, we delete the pair with the key “k2” from the map m:

delete(m, "k2")

When accessing a value in a map, two values are returned. The second value indicates whether the key was present in the map. This is useful for distinguishing between missing keys and keys with “falsy” values like 0 or "", which could evaluate to false in user-defined logic checks. You can use a blank identifier (_) to omit the value if it’s not needed:

_, isThere := m["none"]
fmt.Println("Is there:", isThere) // false