Initial implementation of config file

internal/config.go

@@ -0,0 +1,28 @@
+package magellan
+
+import (
+	"fmt"
+
+	"github.com/bikeshack/magellan/internal/util"
+	"github.com/spf13/viper"
+)
+
+func LoadConfig(path string) error {
+	dir, filename, ext := util.SplitPathForViper(path)
+	// fmt.Printf("dir: %s\nfilename: %s\nextension: %s\n", dir, filename, ext)
+	viper.AddConfigPath(dir)
+	viper.SetConfigName(filename)
+	viper.SetConfigType(ext)
+	// ...no search paths set intentionally, so config has to be set explicitly
+	// ...also, the config file will not save anything
+	// ...and finally, parameters passed to CLI have precedence over config values
+	if err := viper.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+			return fmt.Errorf("config file not found: %w", err)
+		} else {
+			return fmt.Errorf("could not load config file: %w", err)
+		}
+	}
+
+	return nil
+}