Feature: Protonvpn filter servers with FREE_ONLY

internal/configuration/protonvpn.go

@@ -2,6 +2,7 @@ package configuration
 
 import (
 	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/golibs/params"
 )
 
 func (settings *Provider) protonvpnLines() (lines []string) {
@@ -25,6 +26,10 @@ func (settings *Provider) protonvpnLines() (lines []string) {
 		lines = append(lines, lastIndent+"Hostnames: "+commaJoin(settings.ServerSelection.Hostnames))
 	}
 
+	if settings.ServerSelection.FreeOnly {
+		lines = append(lines, lastIndent+"Free only: yes")
+	}
+
 	return lines
 }
 
@@ -71,5 +76,10 @@ func (settings *Provider) readProtonvpn(r reader) (err error) {
 		return err
 	}
 
+	settings.ServerSelection.FreeOnly, err = r.env.YesNo("FREE_ONLY", params.Default("no"))
+	if err != nil {
+		return err
+	}
+
 	return nil
 }