五大必学类库助力Go语言学习之路

package main

import "fmt"

func main() {
    var num1 = 10
    var num2 = 20
    var sum = num1 + num2

    fmt.Printf("num1: %d, num2: %d, sum: %d
", num1, num2, sum)
}

package main

import (
    "fmt"
    "net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, World!")
}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":8080", nil)
}

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/database")
    if err != nil {
        panic(err.Error())
    }
    defer db.Close()

    rows, err := db.Query("SELECT * FROM table")
    if err != nil {
        panic(err.Error())
    }

    defer rows.Close()

    for rows.Next() {
        var id int
        var name string
        err = rows.Scan(&id, &name)
        if err != nil {
            panic(err.Error())
        }

        fmt.Println("ID:", id, "Name:", name)
    }
}

package main

import (
    "encoding/json"
    "fmt"
)

type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

func main() {
    person := Person{Name: "Alice", Age: 30}
    jsonBytes, err := json.Marshal(person)
    if err != nil {
        panic(err.Error())
    }

    fmt.Println(string(jsonBytes))

    var newPerson Person
    err = json.Unmarshal(jsonBytes, &newPerson)
    if err != nil {
        panic(err.Error())
    }

    fmt.Println(newPerson)
}

package main

import (
    "fmt"
    "time"
)

func main() {
    currentTime := time.Now()
    fmt.Println("Current time:", currentTime)

    futureTime := currentTime.AddDate(0, 0, 7)
    fmt.Println("Future time (7 days later):", futureTime)

    layout := "2006-01-02 15:04:05"
    timeStr := currentTime.Format(layout)
    fmt.Println("Formatted time:", timeStr)
}