Go Slices: Why Your Function Isn't Changing What You Think It Is

15 min read · Beginner-friendly · Real code you can paste into Go Playground The bug that confuses every Go beginner You pass your slice to a function. The function changes some values. You print the slice back in main ... and some changes are there, some aren't. Sound familiar? This article explains exactly why — with diagrams, not walls of text. Our data — a fleet of vehicles Two structs, one slice. Everything in this article uses these types. type VehicleType struct { TwoWheeler , ThreeWheeler , FourWheeler bool } type Vehicle struct { Model , Color string Type VehicleType // nested by value — not a pointer } type Fleet [] Vehicle Fill it with two vehicles: fleet := Fleet { { Model : "Bike" , Color : "Red" , Type : VehicleType { TwoWheeler : true }}, { Model : "Car" , Color : "Blue" , Type : VehicleType { FourWheeler : true }}, } What is a slice? (the sticky note model) Before anything else, burn this mental model in — a slice variable is just a 3-field sticky note . The real data l