1. 创建项目

mkdir viper-test
cd viper-test/
go mod init viper-test

go get github.com/spf13/viper@v1.10.0
go get go.uber.org/multierr@v1.11.0
go get github.com/go-playground/validator/v10

2. 项目结构

3. config/init.go

package config

import (
  "fmt"
  "github.com/fsnotify/fsnotify"
  "github.com/go-playground/validator/v10"
  "github.com/spf13/viper"
  "go.uber.org/multierr"
  "os"
  "os/user"
  "path"
  "path/filepath"
  "strings"
)

const PathEnvName = "CONFIG_PATH"
const NameEnvName = "CONFIG_NAME"
const TypeEnvName = "CONFIG_TYPE"
const DefaultName = "config"
const DefaultType = "yaml"

var Config = new(config)

func init() {
  getConfig()
}

type config struct {
  Mode string `mapstructure:"mode" json:"mode" yaml:"mode" validate:"required,oneof=dev staging product"`
  Port int    `mapstructure:"port" json:"port" yaml:"port" validate:"omitempty,gte=0,lte=65535"`
}

func (c *config) String() string {
  return fmt.Sprintf("config{mode=%s, port=%d}", c.Mode, c.Port)
}

func (c *config) Validate() error {
  validate := validator.New()
  if errs := validate.Struct(c); errs != nil {
    var result error
    for _, err := range errs.(validator.ValidationErrors) {
      result = multierr.Append(result, err)
    }
    return result
  }
  return nil
}

func getConfig() {
  v := viper.New()
  for _, path_ := range getPaths() {
    v.AddConfigPath(path_)
  }
  v.SetConfigName(getName())
  v.SetConfigType(getType())
  if err := v.ReadInConfig(); err != nil {
    panic(err.Error())
  }
  if err := v.Unmarshal(Config); err != nil {
    panic(err.Error())
  } else {
    if err := Config.Validate(); err != nil {
      panic(err.Error())
    }
  }
  v.OnConfigChange(func(fsnotify.Event) {
    newConfig := new(config)
    if err := v.Unmarshal(newConfig); err == nil {
      if err := newConfig.Validate(); err == nil {
        Config = newConfig
      }
    }
  })
  v.WatchConfig()
}

func getSubPaths(dir string) []string {
  return []string{dir, path.Join(dir, "config")}
}

func getPaths() []string {
  var configPaths = make([]string, 0)
  // 从环境变量获取
  if paths := os.Getenv(PathEnvName); paths != "" {
    for _, path_ := range strings.Split(paths, string(os.PathListSeparator)) {
      configPaths = append(configPaths, getSubPaths(path_)...)
    }
  }
  // 当前工作目录及其下的 config 目录
  if curDir, err := os.Getwd(); err == nil {
    configPaths = append(configPaths, getSubPaths(curDir)...)
  }
  // 可执行文件所在目录及其下的 config 目录
  if exe, err := os.Executable(); err == nil {
    configPaths = append(configPaths, getSubPaths(filepath.Dir(exe))...)
  }
  // 当前用户的家目录及其下的 config 目录
  if u, err := user.Current(); err == nil {
    configPaths = append(configPaths, getSubPaths(u.HomeDir)...)
  }
  // /etc/config
  configPaths = append(configPaths, getSubPaths(filepath.FromSlash("/etc"))...)
  return configPaths
}

func getName() string {
  if name := os.Getenv(NameEnvName); name != "" {
    return name
  } else {
    return DefaultName
  }
}

func getType() string {
  if type_ := os.Getenv(TypeEnvName); type_ != "" {
    return type_
  } else {
    return DefaultType
  }
}

4. main.go

package main

import (
  . "viper-test/config"
  "fmt"
  "time"
)

func main() {
  for {
    fmt.Println(Config)
    time.Sleep(5 * time.Second)
  }
}

5. config.yaml

mode: product
port: 80

6. 运行

go mod tidy
go run main.go