Adjust error messages to conform to Go best practices (#1400)

https://github.com/golang/go/wiki/CodeReviewComments#error-strings

utils/backup.go

@@ -22,18 +22,18 @@ func Restore(backupFile string, databaseFile string) error {
 
 	data, err := ioutil.ReadFile(backupFile) // nolint
 	if err != nil {
-		return fmt.Errorf("Unable to read backup file %s", err)
+		return fmt.Errorf("unable to read backup file %s", err)
 	}
 
 	gz, err := gzip.NewReader(bytes.NewBuffer(data))
 	if err != nil {
-		return fmt.Errorf("Unable to read backup file %s", err)
+		return fmt.Errorf("unable to read backup file %s", err)
 	}
 	defer gz.Close()
 
 	var b bytes.Buffer
 	if _, err := io.Copy(&b, gz); err != nil { // nolint
-		return fmt.Errorf("Unable to read backup file %s", err)
+		return fmt.Errorf("unable to read backup file %s", err)
 	}
 
 	defer gz.Close()
@@ -41,7 +41,7 @@ func Restore(backupFile string, databaseFile string) error {
 	rawSQL := b.String()
 
 	if _, err := os.Create(databaseFile); err != nil {
-		return errors.New("Unable to write restored database")
+		return errors.New("unable to write restored database")
 	}
 
 	// Create a new database by executing the raw SQL

utils/restendpointhelper.go

@@ -34,7 +34,7 @@ func mapPatternWithRequestURL(pattern string, requestURL string) (map[string]str
 	if len(patternSplit) == len(requestURLSplit) {
 		return zip2D(&patternSplit, &requestURLSplit), nil
 	}
-	return nil, errors.New("The length of pattern and request Url does not match")
+	return nil, errors.New("the length of pattern and request Url does not match")
 }
 
 func readParameter(pattern string, requestURL string, paramName string) (string, error) {
@@ -46,14 +46,14 @@ func readParameter(pattern string, requestURL string, paramName string) (string,
 	if value, exists := all[fmt.Sprintf("{%s}", paramName)]; exists {
 		return value, nil
 	}
-	return "", fmt.Errorf("Parameter with name %s not found", paramName)
+	return "", fmt.Errorf("parameter with name %s not found", paramName)
 }
 
 // ReadRestURLParameter will return the parameter from the request of the requested name.
 func ReadRestURLParameter(r *http.Request, parameterName string) (string, error) {
 	pattern, found := r.Header[restURLPatternHeaderKey]
 	if !found {
-		return "", fmt.Errorf("This HandlerFunc is not marked as REST-Endpoint. Cannot read Parameter '%s' from Request", parameterName)
+		return "", fmt.Errorf("this HandlerFunc is not marked as REST-Endpoint. Cannot read Parameter '%s' from Request", parameterName)
 	}
 
 	return readParameter(pattern[0], r.URL.Path, parameterName)