code: func (c *Config) handleEnvVars() error {
  	// [cloudinary]
  	if c.CloudinaryURI != nil {
  		curi, err := handleQuery(c.CloudinaryURI)
  		if err != nil {
  			return err
  		}
  		c.CloudinaryURI = curi
  	}
  	if len(c.PrependPath) == 0 {
  		// [global]
  		if len(c.ProdTag) > 0 {
  			ptag, err := replaceEnvVars(c.ProdTag)
  			if err != nil {
  				return err
  			}
  			c.PrependPath = cloudinary.EnsureTrailingSlash(ptag)
  		}
  	}
  
  	// [database]
  	if c.MongoURI != nil {
  		muri, err := handleQuery(c.MongoURI)
  		if err != nil {
  			return err
  		}
  		c.MongoURI = muri
  	}
  	return nil
  }
docs: // Parses all structure fields values, looks for any
  // variable defined as ${VARNAME} and substitute it by
  // calling os.Getenv().
  //
  // The reflect package is not used here since we cannot
  // set a private field (not exported) within a struct using
  // reflection.