DSN无效：网络地址未终止（缺少右括号）

Question

I am new to go and backend development. I am trying to use a MySQL database with go to create a REST API.

func getUsers(w http.ResponseWriter, r *http.Request) {
    db, err := sql.Open("mysql", "root:mypassword@tcp(127.0.0.1:3306/test)")
    if err != nil {
        panic(err.Error())
    }
    results, err := db.Query("Select * from users")
    if err != nil {
        panic(err.Error())
    }
    for results.Next() {
        var user User
        err = results.Scan(&user.FirstName)
        if err != nil {
            panic(err.Error)
        }
        fmt.Println(user.FirstName)
    }
    //scores is an array that i have already created just to return dummy data
    json.NewEncoder(w).Encode(scores)
}

I get this error:

http: panic serving [::1]:54508: invalid DSN: network address not terminated (missing closing brace)
goroutine 5 [running]:
net/http.(*conn).serve.func1(0xc42009abe0)
        /usr/local/go/src/net/http/server.go:1726 +0xd0
panic(0x129cea0, 0xc420010ec0)
        /usr/local/go/src/runtime/panic.go:505 +0x229
main.getUsers(0x134bca0, 0xc42011e000, 0xc42011c200)
        /Users/tushar/go/src/github.com/tushar/jump/main.go:62 +0x33f
net/http.HandlerFunc.ServeHTTP(0x1326230, 0x134bca0, 0xc42011e000, 0xc42011c200)
        /usr/local/go/src/net/http/server.go:1947 +0x44
github.com/gorilla/mux.(*Router).ServeHTTP(0xc420110000, 0x134bca0, 0xc42011e000, 0xc42011c200)
        /Users/tushar/go/src/github.com/gorilla/mux/mux.go:162 +0xed
net/http.serverHandler.ServeHTTP(0xc42008aea0, 0x134bca0, 0xc42011e000, 0xc42011c000)
        /usr/local/go/src/net/http/server.go:2694 +0xbc
net/http.(*conn).serve(0xc42009abe0, 0x134bf60, 0xc420062240)
        /usr/local/go/src/net/http/server.go:1830 +0x651
created by net/http.(*Server).Serve
        /usr/local/go/src/net/http/server.go:2795 +0x27b

I am not able to understand the issue.

It works fine when there is no DB query.

EDIT 1: editted sql.Open to change closing braces to root:mypassword@tcp(127.0.0.1:3306)/test works fine when querying

but i get panic while inserting in db

func insertUsers(w http.ResponseWriter, r *http.Request) {
    db, err := sql.Open("mysql", "root:mypassword@tcp(127.0.0.1:3306)/test")
    if err != nil {
        panic(err.Error())
    }
    insert, err := db.Query("Insert into users (personId,firstName,lastName) values(20,tushar,saha)")
    if err != nil {
        panic(err.Error)
    }
    defer insert.Close()
}

this is the error 1

2018/06/23 11:54:10 http: panic serving [::1]:54802: 0x126a8b0
goroutine 19 [running]:
net/http.(*conn).serve.func1(0xc4200aebe0)
        /usr/local/go/src/net/http/server.go:1726 +0xd0
panic(0x129bb20, 0xc42016a020)
        /usr/local/go/src/runtime/panic.go:505 +0x229
main.insertUsers(0x134bc80, 0xc42013c000, 0xc420138200)
        /Users/tushar/go/src/github.com/tushar/jump/main.go:50 +0x15d
net/http.HandlerFunc.ServeHTTP(0x1326218, 0x134bc80, 0xc42013c000, 0xc420138200)
        /usr/local/go/src/net/http/server.go:1947 +0x44
github.com/gorilla/mux.(*Router).ServeHTTP(0xc42012c000, 0x134bc80, 0xc42013c000, 0xc420138200)
        /Users/tushar/go/src/github.com/gorilla/mux/mux.go:162 +0xed
net/http.serverHandler.ServeHTTP(0xc420095040, 0x134bc80, 0xc42013c000, 0xc420138000)
        /usr/local/go/src/net/http/server.go:2694 +0xbc
net/http.(*conn).serve(0xc4200aebe0, 0x134bf40, 0xc42009a200)
        /usr/local/go/src/net/http/server.go:1830 +0x651
created by net/http.(*Server).Serve
        /usr/local/go/src/net/http/server.go:2795 +0x27b

Answer 1

The DSN (i.e. second) argument to the sql.Open() method is malformed.

Only the address portion (127.0.0.1:3306) is supposed to be surrounded by parentheses. You've included the database name within the parentheses as well.

Try this instead:

db, err := sql.Open("mysql", "root:mypassword@tcp(127.0.0.1:3306)/test")

The documented format is:

[username[:password]@][protocol[(address)]]/dbname[?param1=value1&...&paramN=valueN]

---

In response to "EDIT 1"

err.Error() is a method.

In your error handling block for the insert query, you're not calling the method. Instead you're printing out it's memory location.

if err != nil {
    panic(err.Error)
}

If you actually call the method (similar to how you have in the error handling block for the sql.Open()), you'll print out the error message which can point you towards what's wrong.

if err != nil {
    panic(err.Error())
}