Show error from TOML library when parsing fails

.lumerc.sample

@@ -1 +1,11 @@
 access_token = "token"
+
+[colors]
+purple_candy = [ 280.0, 0.29, 0.71 ]
+wasabi = [ 120.0, 1.0, 0.7 ]
+honeydew = [ 120.0, 1.0, 0.97 ]
+green_mist = [ 92.0, 0.72, 0.75 ]
+pea = [ 90.0, 0.42, 0.47 ]
+cat_eye = [ 76.0, 0.74, 0.61 ]
+seagreen = [ 160.0, 1.0, 0.50 ]
+blue_mist = [ 202.0, 0.97, 0.75 ]

cmd/command.go

@@ -100,5 +100,31 @@ func (c *Config) Validate() error {
 	if c.AccessToken == "" {
 		err = errors.New("access_token is not set")
 	}
+
+	if err = c.validateColors(); err != nil {
+		return err
+	}
+
+	return err
+}
+
+func (c *Config) validateColors() (err error) {
+	if len(c.Colors) > 0 {
+		for name, hsb := range c.Colors {
+			if len(hsb) != 3 {
+				return fmt.Errorf("color '%s' needs three values", name)
+			}
+			h, s, b := hsb[0], hsb[1], hsb[2]
+			if h < 0 || h > 360 {
+				return fmt.Errorf("color '%s' hue value must be between 0.0-360.0", name)
+			}
+			if s < 0 || b > 1 {
+				return fmt.Errorf("color '%s' saturation value must be between 0.0-1.0", name)
+			}
+			if b < 0 || b > 1 {
+				return fmt.Errorf("color '%s' brightness value must be between 0.0-1.0", name)
+			}
+		}
+	}
 	return err
 }

cmd/main.go

@@ -24,7 +24,7 @@ func Main(args []string) (int, error) {
 	}
 
 	if _, err := toml.DecodeFile(configPath, &config); err != nil {
-		err = fmt.Errorf("fatal: failed to parse %s", configPath)
+		err = fmt.Errorf("fatal: failed to parse %s; %w", configPath, err)
 		return ExitError, err
 	}