.GO File Format – Versions

Go source code

Go 1.0 was released in March 2012, and a new major release has followed about every six months since. Go 1.27 is the current release. Language changes are listed below, from the release notes and the Language versions appendix of the specification.

The Go 1 compatibility promise

Programs written to the Go 1 specification are intended to keep compiling and running correctly, unchanged, over the lifetime of that specification. The promise has stated exceptions: security problems, unspecified behaviour, specification errors, compiler or library bugs, unkeyed struct literals of imported types, method additions that conflict with an embedded type, dot imports that gain a conflicting name, and code using unsafe. A program’s language version is the version it was written for, so old code keeps its old meaning.

How the language version is chosen

In a module, the go directive sets the language version for its packages. A //go:build line with a go1.N term can lower the version for one file, in modules at Go 1.21 or later. The compiler rejects features newer than the language version in force: a file containing 0b1011 is rejected below Go 1.13.

Language changes that alter behaviour, such as per-iteration loop variables in Go 1.22, apply according to the language version, so an older module keeps its previous behaviour.

Releases

ReleaseDateLanguage changes
Go 1.028 March 2012The first stable release, and the base of the compatibility promise
Go 1.113 May 2013Method values. Terminating statements relax the final-return rule. Integer division by constant zero is a compile error. Surrogate halves are excluded from string and rune literals
Go 1.21 December 2013Three-index slices. Use of nil pointers is guaranteed to trigger a run-time panic
Go 1.318 June 2014None. The memory model gained a rule on buffered channels
Go 1.410 December 2014for range x without variables. Method calls on **T disallowed
Go 1.519 August 2015Element type elision applies to map keys in composite literals
Go 1.617 February 2016None
Go 1.715 August 2016Terminating statements consider the final non-empty statement
Go 1.816 February 2017Struct tags ignored in conversions. The specification requires only 16-bit exponents in floating-point constants
Go 1.924 August 2017Type aliases. Rules for fused floating-point operations
Go 1.1016 February 2018Clarifications: shifts of untyped constants allow x[1.0 << s], and method expressions accept any type expression as a receiver
Go 1.1124 August 2018None. Modules arrive as a preliminary feature
Go 1.1225 February 2019None
Go 1.133 September 2019Number literal prefixes 0b and 0o, hexadecimal floats, i suffix on any literal, digit separators. Signed shift counts
Go 1.1425 February 2020Embedded interfaces may overlap, with identical signatures
Go 1.1511 August 2020None
Go 1.1616 February 2021None. //go:embed arrives through the go command
Go 1.1716 August 2021Slice to array pointer conversions. unsafe.Add and unsafe.Slice
Go 1.1815 March 2022Generics: type parameters, constraints, the ~ token. Predeclared any and comparable
Go 1.192 August 2022A correction to the scope of type parameters in method declarations. The memory model was revised
Go 1.201 February 2023Slice to array conversions. unsafe.SliceData, String and StringData. Field and element comparison order defined. Comparable types satisfy comparable
Go 1.218 August 2023min, max and clear. Package initialisation order made exact. More powerful type inference. panic(nil) becomes a run-time panic
Go 1.226 February 2024Per-iteration for loop variables. Range over integers
Go 1.2313 August 2024Range over iterator functions
Go 1.2411 February 2025Generic type aliases
Go 1.2512 August 2025None affecting programs. The specification dropped the notion of core types in favour of dedicated prose
Go 1.2610 February 2026new accepts an expression. A generic type may refer to itself in its type parameter list
Go 1.2719 August 2026Generic methods. Struct literal keys may be any valid field selector. Function type inference applies wherever a generic function is assigned or converted to a function type

Notes on changes that affect old code

  • Go 1.22 loop variables. Each iteration has its own variables. Code that depended on sharing between iterations, usually a bug, behaves differently once its module moves to a language version of 1.22 or later.
  • Go 1.21 and panic(nil). panic with a nil value now panics with *runtime.PanicNilError. A program whose main package is in a module declaring go 1.20 or earlier keeps the old behaviour, because GODEBUG=panicnil=1 is then set automatically.
  • Go 1.21 and go lines. The go line became a strict minimum, and the go command can fetch a newer toolchain when required.
  • Go 1.18 fixes. Variables set inside a function literal but never used are now rejected as unused.