Use env lib, add PROXY_PORT ENV variable

vendor/github.com/caarlos0/env/examples/first.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strings"
+	"time"
+
+	"github.com/caarlos0/env"
+)
+
+type config struct {
+	Home         string        `env:"HOME"`
+	Port         int           `env:"PORT" envDefault:"3000"`
+	IsProduction bool          `env:"PRODUCTION"`
+	Hosts        []string      `env:"HOSTS" envSeparator:":"`
+	Duration     time.Duration `env:"DURATION"`
+	ExampleFoo   Foo           `env:"EXAMPLE_FOO"`
+}
+
+type Foo struct {
+	Name string
+}
+
+func main() {
+	cfg := config{}
+
+	// Parse for built-in types
+	if err := env.Parse(&cfg); err != nil {
+		log.Fatal("Unable to parse envs: ", err)
+	}
+
+	// OR w/ a custom parser for `Foo`
+	//
+	// if err := env.ParseWithFuncs(&cfg, env.CustomParsers{
+	// 	reflect.TypeOf(Foo{}): fooParser,
+	// }); err != nil {
+	// 	log.Fatal("Unable to parse envs: ", err)
+	// }
+
+	fmt.Printf("%+v\n", cfg)
+}
+
+func fooParser(value string) (interface{}, error) {
+	return Foo{
+		Name: strings.ToUpper(value),
+	}, nil
+}