使用 viper 从 envfile 中读取配置

Question

我不太明白毒蛇的工作原理。这是我的代码：

configuration.go

var Config *Configuration

type ServerConfiguration struct {
    Port string
}

type Configuration struct {
    Server   ServerConfiguration
}

func Init() {
    var configuration *Configuration
    viper.SetConfigFile(".env")
    viper.AutomaticEnv()
    if err := viper.ReadInConfig(); err != nil {
        log.Fatalf("Error reading config file, %s", err)
    }

    err := viper.Unmarshal(&configuration)
    if err != nil {
        log.Fatalf("Unable to decode into struct, %v", err)
    }

    Config = configuration
}

func GetConfig() *Configuration {
    return Config
}

.env SERVER_PORT=:4747

问题是 Unmarshal 不起作用例如，当我使用 configuration.Server.Port 时，它是空的

Answer 1

spf13/viper predominantly uses mapstructure package to convert between one native Go type to another i.e. when un-marshaling. The package internally uses map[string]interface{} type to store your config (see viper.go - L1327). After that depending on the config type (your case being env), viper calls the right parsing package to store your config values. For envfile type, it uses subosito/gotenv to put in the above said map type (see viper.go - L1501)

问题的症结在于如何让 viper 将映射中的此配置解组为您选择的结构。这是 mapstructure 包的用武之地，用于将地图解组为您定义的嵌套结构。此时你有两个选择

将配置解组为 map[string]interface{} 类型，然后使用 mapstructure
使用DecodeHookFunc as a 2nd argument to your method to unmarshal your config (See viper.go - L904)

为了简单起见，你可以做一个，根据我用你的例子复制的一个简单的例子，可以在下面完成

package main

import (
    "fmt"
    "github.com/mitchellh/mapstructure"
    "github.com/spf13/viper"
)

type ServerConfiguration struct {
    Port string `mapstructure:"server_port"`
}

type Configuration struct {
    Server ServerConfiguration `mapstructure:",squash"`
}

func main() {
    var result map[string]interface{}
    var config Configuration
    viper.SetConfigFile(".env")
    if err := viper.ReadInConfig(); err != nil {
        fmt.Printf("Error reading config file, %s", err)
    }

    err := viper.Unmarshal(&result)
    if err != nil {
        fmt.Printf("Unable to decode into map, %v", err)
    }

    decErr := mapstructure.Decode(result, &config)

    if decErr != nil {
        fmt.Println("error decoding")
    }

    fmt.Printf("config:%+v\n", config)
}

您可以根据您的实际用例自定义此工作示例。有关嵌入式结构的 mapstructure squash 标签的更多信息，请参见 here

使用 viper 从 envfile 中读取配置

Using viper to read config from envfile

go

viper-go