Like slices, maps hold references to an underlying data structure. So by assigning its value to another variable, only the reference will be passed. To copy the map, it is necessary to create another map and copy each value:
// Create the original map
originalMap := make(map[string]int)
originalMap["one"] = 1
originalMap["two"] = 2
// Create the target map
targetMap := make(map[string]int)
// Copy from the original map to the target map
for key, value := range originalMap {
targetMap[key] = value
}