Simpler code with early returns: "Guard Clauses"

This is how "ideomatic Go" (or any other code) should like, simpler.

Guard Clauses: Simplifying Code with Early Returns | by Vaibhav Mojidra | Medium

Guard clauses (or early returns) are conditional statements placed at the beginning of a function that exit early if specific conditions are not met, reducing nested if-else structures. They improve readability by separating error handling and validations from the main logic

JS

function getMemberDiscount(member) {
  if (member) {
    if (member.isPremium) {
      return "20% off";
    } else {
      return "10% off";
    }
  } else {
    return "No discount";
  }
}

=>
function getMemberDiscount(member) {
  // Guard clauses
  if (!member) return "No discount";
  if (!member.isPremium) return "10% off";
  // Main logic (no nesting)
  return "20% off";
}

In modern programming languages like C#, Java, and Dart, guard clauses can be used within switch expressions to add additional conditions to a pattern match. These are often called case guards or when clauses. 

C#
public static string GetShippingCategory(int weight) => weight switch
{
    <= 0                  => "Invalid weight",          // Base pattern
    var w when w < 5      => "Lightweight",             // Guard clause (when w < 5)
    var w when w < 20     => "Standard",                // Guard clause (when w < 20)
    _                     => "Heavy / Freight"          // Discard (default)
};

Java

static String checkString(Object obj) {
    return switch (obj) {
        case String s when s.length() == 1 -> "Short string"; // Guard clause
        case String s                      -> "Long string";  // General pattern
        default                            -> "Not a string";
    };
}

Guard Clauses: Simplifying Code with Early Returns | by Vaibhav Mojidra | Medium