Standard Library Hits

High-frequency standard library packages. Results appear in the same fence: same-line // comments when short, multiline // blocks below the sample when not.

strings Builder

Efficient string building.

var b strings.Builder
b.WriteString("a")
b.WriteString("b")
b.String()  // "ab"

strconv

Parse and format numbers.

n, err := strconv.Atoi("42")
n  // 42
// err == nil
strconv.Itoa(7)  // "7"

time Format

Reference layout Mon Jan 2 15:04:05 MST 2006.

t := time.Date(2020, 1, 2, 0, 0, 0, 0, time.UTC)
t.Format(time.RFC3339)  // "2020-01-02T00:00:00Z"

encoding json

Marshal and unmarshal.

b, _ := json.Marshal(struct{ A int }{A: 1})
string(b)  // {"A":1}

io Copy

Stream copy between reader and writer.

// n, err := io.Copy(dst, src)

bytes Buffer

In-memory buffer.

var buf bytes.Buffer
buf.WriteString("x")
buf.String()  // "x"

fmt Sprintf

Formatting without print.

fmt.Sprintf("%s-%d", "a", 1)  // "a-1"

sort Slice

Sort helpers.

s := []int{3, 1, 2}
sort.Ints(s)
s  // [1 2 3]

regexp

Compile once when possible.

re := regexp.MustCompile("^\\d+$")
re.MatchString("42")  // true

os ReadFile

Read whole small files.

// b, err := os.ReadFile("f.txt")

filepath Join

Join paths portably.

filepath.Join("a", "b")  // a/b (OS sep)

slog

Structured logging (Go 1.21+).

// slog.Info("hello", "user", "ada")

slices Contains

slices package helpers (Go 1.21+).

// slices.Contains([]int{1, 2}, 2) == true

cmp Compare

Ordered compares (Go 1.21+).

// cmp.Compare(1, 2) == -1

sync Map Note

sync.Map for special cases - prefer Mutex map usually.

// var m sync.Map

Related

• Net HTTP Essentials - json over HTTP
• Syntax and Basics - uses these packages
• Error Handling - fmt.Errorf

External Related Links

• Go Standard Library Documentation - Complete reference for the standard library.
• pkg.go.dev - Official package documentation and discovery site.
• Go by Example - Annotated practical code examples.
• The Go Programming Language (Paperback) - Donovan & Kernighan paperback.
• Learning Go (2nd Edition, O'Reilly) - Jon Bodner on O'Reilly.

Stack versions: Go 1.26.x · chi/gin/echo latest (verify at build)