tl;dr: Go 1.27's headline feature is generic methods, allowing method declarations to have their own type parameters independent of the receiver (though interfaces still can't declare them). Other notable additions include a standard library `uuid` package, `encoding/json/v2` graduating from experimental status (with v1 now backed by v2), post-quantum ML-DSA signatures, an experimental portable `simd` package, promoted-field struct literal selectors, and generalized function type inference. Performance improvements include size-specialized memory allocation (~30% faster for small allocations) and three new compiler optimizations enabled by default.