updater: refactoring and set DNS server correctly

- Fix CLI operation not setting DNS server
- Fix periodic operation not setting DNS server
- Set DNS address for resolution once at start for both CLI and periodic operation
- Inject resolver to each provider instead of creating it within
- Use resolver settings on every call to `.Resolve` method, instead of passing it to constructor
- Move out minServers check from resolver

internal/provider/expressvpn/connection_test.go

@@ -89,7 +89,8 @@ func Test_Provider_GetConnection(t *testing.T) {
 
 			unzipper := (common.Unzipper)(nil)
 			warner := (common.Warner)(nil)
-			provider := New(storage, randSource, unzipper, warner)
+			parallelResolver := (common.ParallelResolver)(nil)
+			provider := New(storage, randSource, unzipper, warner, parallelResolver)
 
 			if testCase.panicMessage != "" {
 				assert.PanicsWithValue(t, testCase.panicMessage, func() {

internal/provider/expressvpn/provider.go

@@ -17,12 +17,13 @@ type Provider struct {
 }
 
 func New(storage common.Storage, randSource rand.Source,
-	unzipper common.Unzipper, updaterWarner common.Warner) *Provider {
+	unzipper common.Unzipper, updaterWarner common.Warner,
+	parallelResolver common.ParallelResolver) *Provider {
 	return &Provider{
 		storage:         storage,
 		randSource:      randSource,
 		NoPortForwarder: utils.NewNoPortForwarding(providers.Expressvpn),
-		Fetcher:         updater.New(unzipper, updaterWarner),
+		Fetcher:         updater.New(unzipper, updaterWarner, parallelResolver),
 	}
 }
 

internal/provider/expressvpn/updater/resolve.go

@@ -6,13 +6,14 @@ import (
 	"github.com/qdm12/gluetun/internal/updater/resolver"
 )
 
-func newParallelResolver() *resolver.Parallel {
+func parallelResolverSettings(hosts []string) (settings resolver.ParallelSettings) {
 	const (
 		maxFailRatio = 0.1
 		maxNoNew     = 1
 		maxFails     = 2
 	)
-	settings := resolver.ParallelSettings{
+	return resolver.ParallelSettings{
+		Hosts:        hosts,
 		MaxFailRatio: maxFailRatio,
 		Repeat: resolver.RepeatSettings{
 			MaxDuration: time.Second,
@@ -21,5 +22,4 @@ func newParallelResolver() *resolver.Parallel {
 			SortIPs:     true,
 		},
 	}
-	return resolver.NewParallelResolver(settings)
 }

internal/provider/expressvpn/updater/servers.go

@@ -21,7 +21,8 @@ func (u *Updater) FetchServers(ctx context.Context, minServers int) (
 		hosts[i] = servers[i].Hostname
 	}
 
-	hostToIPs, warnings, err := u.presolver.Resolve(ctx, hosts, minServers)
+	resolveSettings := parallelResolverSettings(hosts)
+	hostToIPs, warnings, err := u.presolver.Resolve(ctx, resolveSettings)
 	for _, warning := range warnings {
 		u.warner.Warn(warning)
 	}

internal/provider/expressvpn/updater/updater.go

@@ -10,10 +10,11 @@ type Updater struct {
 	warner    common.Warner
 }
 
-func New(unzipper common.Unzipper, warner common.Warner) *Updater {
+func New(unzipper common.Unzipper, warner common.Warner,
+	parallelResolver common.ParallelResolver) *Updater {
 	return &Updater{
 		unzipper:  unzipper,
-		presolver: newParallelResolver(),
+		presolver: parallelResolver,
 		warner:    warner,
 	}
 }