[searcher] Add SearchOption and handle host error

Author: hezhizhen

internal/searcher/client.go

@@ -31,16 +31,19 @@ var cachedClient *client
 
 func Client() *client {
 	if cachedClient == nil {
-		endpoint, _ := url.JoinPath(searchHost(), "search")
-		// TODO: how to handle error
+		endpoint, err := url.JoinPath(searchHost(), "search")
+		if err != nil {
+			// TODO: better handle this error when users use invalid custom hosts
+			panic(err)
+		}
 		cachedClient = &client{
 			endpoint: endpoint,
 		}
 	}
 	return cachedClient
 }
 
-func (c *client) Search(query string, options ...func() string) (*SearchResult, error) {
+func (c *client) Search(query string, options ...SearchOption) (*SearchResult, error) {
 	if query == "" {
 		return nil, fmt.Errorf("query should not be empty")
 	}
@@ -54,7 +57,10 @@ func (c *client) Search(query string, options ...func() string) (*SearchResult,
 	return execSearch(searchURL)
 }
 
-func WithVersion(version string) func() string {
+// SearchOption returns a string for query to be appended to the endpoint
+type SearchOption func() string
+
+func WithVersion(version string) SearchOption {
 	return func() string {
 		return "&v=" + url.QueryEscape(version)
 	}