How to Use Maps in Go – Best Practices for Key-Value Data

What is a Map?

A map is Go's built-in hash table type, storing unordered key-value pairs.

Declaring and Using Maps

ages := map[string]int{
    "Alice": 25,
    "Bob":   30,
}

ages["Charlie"] = 35        // add a new key
fmt.Println(ages["Alice"])  // 25

value, exists := ages["Dave"]
if !exists {
    fmt.Println("Dave not found")
}

delete(ages, "Bob")

Best Practices

• Always check for existence using the two-value form (value, ok := map[key]) to distinguish a missing key from a zero value.
• Maps in Go are unordered — never rely on iteration order when looping with for key, value := range map.
• Use make(map[string]int) to initialize an empty map before adding keys, to avoid a nil map panic on write.