[Summary] Several common golang dynamic settings methods

In the Go language, we often need to dynamically set some configurations, such as reading configuration files, reading configurations from environment variables, etc. This article will introduce several common dynamic settings.

Reading configuration files

Reading configuration files is a common dynamic setting method. In Go language, we can use [viper](https://github.com/spf13 /viper) library to easily read configuration files. The following is a simple example:

package main

import (
    "fmt"

    "github.com/spf13/viper"
)

func main() {
    viper.SetConfigName("config") // 配置文件名
    viper.SetConfigType("yaml")   // 配置文件类型
    viper.AddConfigPath(".")      // 配置文件路径
    err := viper.ReadInConfig()   // 读取配置文件
    if err != nil {
        fmt.Printf("Read config file error: %v\n", err)
        return
    }

    fmt.Println(viper.GetString("name")) // 从配置文件中读取配置项
}

In the above code, we first set the name, type and path of the configuration file, and then call the viper.ReadInConfig() method to read the configuration file, and finally obtain the value of the configuration item through the viper.GetString() method.

Read configuration from environment variables

In actual development, sometimes we need to read some configuration information from environment variables. In the Go language, we can use the Getenv() method of the os package to get the value of the environment variable. The following is an example:

package main

import (
    "fmt"
    "os"
)

func main() {
    name := os.Getenv("APP_NAME")
    if name == "" {
        name = "unknown"
    }

    fmt.Printf("Application name: %s\n", name)
}

In the above code, we first obtain the value of the environment variable APP_NAME through the os.Getenv() method. If the environment variable does not If exists, the default value unknown is used.

Set configuration items through command line parameters

Sometimes we need to specify some configuration information through command line parameters. In Go language, we can use the flag package to parse command line parameters. The following is an example:

package main

import (
    "flag"
    "fmt"
)

func main() {
    var name string
    flag.StringVar(&name, "name", "unknown", "Application name")
    flag.Parse()

    fmt.Printf("Application name: %s\n", name)
}

In the above code, we first define a name variable, and then call the flag.StringVar() method to parse the command line parameters -name and set the default value to unknown, and finally use the flag.Parse() method to parse the command line parameters and obtain their values.

Conclusion

This article introduces several common dynamic setting methods, including reading configuration information from configuration files, environment variables and command line parameters. Using these methods can help us easily and dynamically set the configuration information of the program.

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