Why can't my Go program connect to the database?

When developing Go language, we often involve the operation of connecting to the database. However, in actual development, we often encounter the problem of being unable to connect to the database, which not only affects our work efficiency, but also wastes a lot of time and energy.

So, why can’t our Go program connect to the database? This article will analyze and answer this question.

1. Verify the connection parameters of the database

If you cannot connect to the database, the best way is to verify that the connection parameters are correct, including the database address, username, password and Database name, etc. Please double check that the connection parameters are correct and make sure the database is started.

In the Go language, we usually use the database/sql package in the standard library to operate the database. For the MySQL database, we need to use the mysql driver package and use the mysql.Open() function to create a new database connection. The following is a sample code:

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

func main() {
    db, err := sql.Open("mysql", "username:password@tcp(host:3306)/database")
    if err != nil {
        fmt.Println(err)
        return
    }
    err = db.Ping()
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println("Successfully connected to database!")
}

In the above code, we use the mysql.Open() function to create a new database connection, and use the db.Ping() function to check whether the connection is successful.

2. Verify the port number of the database

If your Go program cannot connect to the database, it may be because your database port number is incorrect. By default, the MySQL database uses port 3306. If your database uses other port numbers, then you need to specify the correct port number in the connection parameters. Please note that some databases will use other default ports, such as PostgreSQL using port 5432.

3. Verify network connection

If your Go program cannot connect to the database, there may be a problem with the network connection. First, you need to make sure your network connection is normal, which can be tested by ping or telnet command. Second, you need to make sure your firewall or network security device is not blocking the database port.

If you are using a cloud database service, such as Alibaba Cloud RDS or AWS RDS, you need to check the network configuration of the database instance to ensure that it can be accessed externally. Normally, these cloud database services will provide a public IP address and port, and you need to use this information to connect to the database.

4. Check database account permissions

If your Go program cannot connect to the database, it may be because your database account does not have sufficient permissions. Please check whether your database account has permission to connect to the database, and whether it has read permission to the data table, view or stored procedure that needs to be accessed.

In the MySQL database, you can use the following command to view the permissions of the account:

SHOW GRANTS FOR 'username'@'host';

If your account does not have sufficient permissions, you need to authorize the account in the database.

5. Check the database connection pool

If your Go program uses a connection pool, then you need to check whether the maximum number of connections in the connection pool is correct, and make sure that the connection pool does not Being filled. When the connection pool is full, new connection requests will be blocked until a connection becomes available.

In the Go language, the database/sql package has provided us with a default connection pool, and it will automatically expand when there are too many connections. Of course, in high concurrency situations, we can manually set the maximum number of connections in the connection pool to avoid too many connections causing the program to run slowly.

Summary

The above are several common reasons why the Go program cannot connect to the database. We need to investigate according to the actual situation. When encountering the problem of being unable to connect to the database, we should check the connection parameters, port number, network connection, account permissions, connection pool and other information as soon as possible in order to solve the problem in time and improve our work efficiency.

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