Read Config File
Json
If your config file only contains a few of fields, and you don't want to install external modules, the easiest way is just using the json file.
Suppose we have a config file like below:
{
"host": "127.0.0.1",
"port": 8080,
"redis": {
"keyprefix": "golang",
"server": "127.0.0.1:6079"
}
}
Then we can define our structs and parse it in Go:
type rediscfg struct {
KeyPrefix string `json:"keyprefix"`
Server string `json:"server"`
}
type config struct {
Host string `json:"host"`
Port int `json:"port"`
Redis rediscfg `json:"redis"`
}
func main() {
content, _ := ioutil.ReadFile("./config.json")
var cfg config
json.Unmarshal(content, &cfg)
}
Read Json with Viper
First we need to install viper:
$ go get github.com/spf13/viper
Then read it with Viper
import "github.com/spf13/viper"
type rediscfg struct {
KeyPrefix string `json:"keyprefix" mapstructure:"keyprefix"`
Server string `json:"server" mapstructure:"server"`
}
type config struct {
Host string `json:"host" mapstructure:"host"`
Port int `json:"port" mapstructure:"port"`
Redis rediscfg `json:"redis" mapstructure:"redis"`
}
func main() {
viper.SetConfigFile("./config.json")
var cfg config
if err := viper.ReadInConfig(); err != nil {
log.Fatalln("Failed to read config file")
}
viper.Unmarshal(&cfg)
}
An easier way is just use viper.Get function, which you don't even need to define the config struct.
func main() {
viper.SetConfigFile("./config.json")
var cfg config
if err := viper.ReadInConfig(); err != nil {
log.Fatalln("Failed to read config file")
}
fmt.Println("Host:", viper.GetString("host"))
fmt.Println("Redis Server:", viper.GetString("redis.server"))
}
Use YAML
With viper we can also use the yaml format. Suppose we have the yaml file like this:
host: 127.0.0.1
port: 8080
redis:
keyprefix: golang
server: 127.0.0.1:6379
The beauty is we only need to change the config file path:
Without defining the config struct:
func main() {
viper.SetConfigFile("./config.yaml")
var cfg config
if err := viper.ReadInConfig(); err != nil {
log.Fatalln("Failed to read config file")
}
fmt.Println("Host:", viper.GetString("host"))
fmt.Println("Redis Server:", viper.GetString("redis.server"))
}
With defining the config struct:
import "github.com/spf13/viper"
type rediscfg struct {
KeyPrefix string `json:"keyprefix" mapstructure:"keyprefix"`
Server string `json:"server" mapstructure:"server"`
}
type config struct {
Host string `json:"host" mapstructure:"host"`
Port int `json:"port" mapstructure:"port"`
Redis rediscfg `json:"redis" mapstructure:"redis"`
}
func main() {
viper.SetConfigFile("./config.yaml")
var cfg config
if err := viper.ReadInConfig(); err != nil {
log.Fatalln("Failed to read config file")
}
viper.Unmarshal(&cfg)
}