The way of string concatenation cannot be detected correctly

[wxzkenny]

 the code as following：

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/lib/pq"
)

func main() {
    db, err := sql.Open("postgres", "user=postgres password=password dbname=mydb sslmode=disable")
    if err!= nil {
        panic(err)
    }
    defer db.Close()

    var username string
    fmt.Println("请输入用户名:")
    fmt.Scanln(&username)

    var query string = "SELECT * FROM users WHERE username = '" + username + "'"
    rows, err := db.Query(query)
    if err!= nil {
        panic(err)
    }
    defer rows.Close()

    // 处理查询结果
}