import "github.com/kelseyhightower/envconfig"See godoc
Set some environment variables:
export MYAPP_DEBUG=false
export MYAPP_PORT=8080
export MYAPP_USER=Kelsey
export MYAPP_RATE="0.5"
export MYAPP_TIMEOUT="3m"
export MYAPP_USERS="rob,ken,robert"Write some code:
package main
import (
"fmt"
"log"
"time"
"github.com/kelseyhightower/envconfig"
)
type Specification struct {
Debug bool
Port int
User string
Users []string
Rate float32
Timeout time.Duration
}
func main() {
var s Specification
err := envconfig.Process("myapp", &s)
if err != nil {
log.Fatal(err.Error())
}
format := "Debug: %v\nPort: %d\nUser: %s\nRate: %f\nTimeout: %s\n"
_, err = fmt.Printf(format, s.Debug, s.Port, s.User, s.Rate)
if err != nil {
log.Fatal(err.Error())
}
fmt.Println("Users:")
for _, u := range s.Users {
fmt.Printf(" %s\n", u)
}
}Results:
Debug: false
Port: 8080
User: Kelsey
Rate: 0.500000
Timeout: 3m0s
Users:
rob
ken
robertEnvconfig supports the use of struct tags to specify alternate, default, and required environment variables.
For example, consider the following struct:
type Specification struct {
MultiWordVar string `envconfig:"multi_word_var"`
DefaultVar string `default:"foobar"`
RequiredVar string `required:"true"`
IgnoredVar string `ignored:"true"`
}Envconfig will process value for MultiWordVar by populating it with the
value for MYAPP_MULTI_WORD_VAR.
export MYAPP_MULTI_WORD_VAR="this will be the value"
# export MYAPP_MULTIWORDVAR="and this will not"If envconfig can't find an environment variable value for MYAPP_DEFAULTVAR,
it will populate it with "foobar" as a default value.
If envconfig can't find an environment variable value for MYAPP_REQUIREDVAR,
it will return an error when asked to process the struct.
If envconfig can't find an environment variable in the form PREFIX_MYVAR, and there
is a struct tag defined, it will try to populate your variable with an environment
variable that directly matches the envconfig tag in your struct definition:
export SERVICE_HOST=127.0.0.1
export MYAPP_DEBUG=truetype Specification struct {
ServiceHost string `envconfig:"SERVICE_HOST"`
Debug bool
}Envconfig won't process a field with the "ignored" tag set to "true", even if a corresponding environment variable is set.
envconfig supports supports these struct field types:
- string
- int8, int16, int32, int64
- bool
- float32, float64
Embedded structs using these fields are also supported.
Any field whose type (or pointer-to-type) implements envconfig.Decoder can
control its own deserialization:
export DNS_SERVER=8.8.8.8type IPDecoder net.IP
func (ipd *IPDecoder) Decode(value string) error {
*ipd = IPDecoder(net.ParseIP(value))
return nil
}
type DNSConfig struct {
Address IPDecoder `envconfig:"DNS_SERVER"`
}
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