In which cases is it safe to read data from a Map that has not yet been explicitly initialized?

In Go, reading from a map that has not been explicitly initialized (i.e., is nil) is safe but with limitations.

If the map is nil, then:

• Reading a value by key returns the zero value of the element type and false when checking for the key's existence.
• Writing (assigning) to such a map will cause a panic.

Example:

var m map[string]int // m == nil

value, ok := m["key"] // safe, value == 0, ok == false

// m["key"] = 10 // panic: assignment to entry in nil map

Thus, it is safe to read from a map if it is not initialized, but you cannot write to it. To write, you need to initialize the map beforehand using make.