[golang syntax] map common errors golang panic: assignment to entry in nil map

map Statement of

var map_variable map[key_data_type]`value_data_type`

After declaration map The default value of is nil

map Most of the operations on , Including finding 、 Delete 、len and range The cycle can work safely in nil It's worth it map On , Their behavior and an empty map similar . But to one nil It's worth it map Storing elements will result in a panic abnormal ：

golang panic: assignment to entry in nil map

In the map Before saving data, you must use golang Built in make Function creation map.

map_variable := make(map[key_data_type]value_data_type)

If not initialized map, Then create a nil map.nil map Cannot be used to store key value pairs

Combine the above into one sentence

//  initialization  +  Integration of assignment 
m := map[string]string{
    "a": "aa",
    "b": "bb",
}