allow multiple docker providers, added file provider support

src/go-proxy/file_provider.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/fsnotify/fsnotify"
+	"gopkg.in/yaml.v3"
+)
+
+func (p *Provider) getFileProxyConfigs() ([]*ProxyConfig, error) {
+	path := p.Value
+
+	if _, err := os.Stat(path); err == nil {
+		data, err := os.ReadFile(path)
+		if err != nil {
+			return nil, fmt.Errorf("unable to read config file %q: %v", path, err)
+		}
+		configMap := make(map[string]ProxyConfig, 0)
+		configs := make([]*ProxyConfig, 0)
+		err = yaml.Unmarshal(data, &configMap)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse config file %q: %v", path, err)
+		}
+
+		for alias, cfg := range configMap {
+			cfg.Alias = alias
+			err = cfg.SetDefault()
+			if err != nil {
+				return nil, err
+			}
+			configs = append(configs, &cfg)
+		}
+		return configs, nil
+	} else if !os.IsNotExist(err) {
+		return nil, fmt.Errorf("file not found: %s", path)
+	} else {
+		return nil, err
+	}
+}
+
+func (p *Provider) grWatchFileChanges() {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		p.Errorf("Watcher", "unable to create file watcher: %v", err)
+	}
+	defer watcher.Close()
+
+	if err = watcher.Add(p.Value); err != nil {
+		p.Errorf("Watcher", "unable to watch file %q: %v", p.Value, err)
+		return
+	}
+
+	for {
+		select {
+		case <-p.stopWatching:
+			return
+		case event, ok := <-watcher.Events:
+			if !ok {
+				return
+			}
+			switch {
+			case event.Has(fsnotify.Write):
+				p.Logf("Watcher", "file change detected", p.name)
+				p.StopAllRoutes()
+				p.BuildStartRoutes()
+			case event.Has(fsnotify.Remove), event.Has(fsnotify.Rename):
+				p.Logf("Watcher", "file renamed / deleted", p.name)
+				p.StopAllRoutes()
+			}
+		case err := <-watcher.Errors:
+			p.Errorf("Watcher", "File watcher error: %s", p.name, err)
+		}
+	}
+}