mysql - 在另一个函数中使用 sql 连接

Question

如何在 main 函数中初始化 mysql 连接并将其放置在另一个函数中？或者在另一个地方初始化连接并在任何地方使用它？

像下面这样的东西(这个例子错了!)

package main

import (
    "fmt"
    "net/http"

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

func indexHandler(w http.ResponseWriter, r *http.Request) {
      stmt, err := db.Prepare("INSERT userinfo SET username=?,departname=?,created=?")
      res, err := stmt.Exec("test", "test", "test")
}

func main() {
    db, err := sql.Open("mysql", "connection")
    if err != nil {
        panic(err)
    }
    http.HandleFunc("/", indexHandler)
    http.ListenAndServe(":3000", nil)
}

谢谢!

Answer 1

使其全局化:

var db *sql.DB

func indexHandler(w http.ResponseWriter, r *http.Request) {
    stmt, err := db.Prepare(...
    ...
}

func main() {
    var err error
    db, err = sql.Open("mysql", "connection")
    ...

或创建处理程序作为闭包:

func createIndexHandler(db *sql.DB) (func (http.ResponseWriter, *http.Request)) {
    return func(w http.ResponseWriter, r *http.Request) {
        stmt, err := db.Prepare(...
        ...
    }
}

func main() {
    db, err := sql.Open("mysql", "connection")
    ...
    http.HandleFunc("/", createIndexHandler(db))