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Yesterday, the Go team announced the release of Go 1.13. This version comes with uniform and modernized number literals, support for error wrapping, TLS 1.3 on by default, improved modules support, and much more. Also, the go command now uses module mirror and checksum database by default.

Key updates in Go 1.13

TLS 1.3 enabled by default

Go 1.13 comes with Transportation Layer Security (TLS) 1.3 support in the crypto/tls package enabled by default. If you wish to disable it, add tls13=0 to the GODEBUG environment variable. The team shared that the option to opt-out will be removed in Go 1.14.

Uniform and modernized number literal prefixes

Go 1.13 introduces optional prefixes for binary and octal integer literals, hexadecimal floating-point literals, and imaginary literals. The 0b or 0B prefix will indicate a binary integer literal, for instance, ‘0b1011.’ The 0o or 0O prefix will indicate an octal integer literal such as 0o660. The 0 prefix used in previous versions is also valid. The 0x or 0X prefix will be used to represent the mantissa of a floating-point number in hexadecimal format such as 0x1.0p-1021. The imaginary suffix (i) can be used with any integer or floating-point literal.


To improve readability, the digits of any number literal can now be separated using underscores, for instance,  1_000_000, 0b_1010_0110. It can also be used between the literal prefix and the first digit.

Read also: The Go team shares new proposals planned to be implemented in Go 1.13 and 1.14

Module mirror to download modules

Starting with Go 1.13, the go command will download and authenticate modules using the module mirror and checksum database by default. A module mirror is a module proxy that fetches modules from origin servers and then caches them for use in future requests. This enables the mirror to serve the source code even when the origin servers are down.

The go command will use the module mirror maintained by the Go team, which is served at https://proxy.golang.org. In case you are using an earlier version of the go command, you can use this service by setting ‘GOPROXY=https://proxy. golang.org’ in your local environment.

Checksum database to authenticate modules

The go command maintains two Go modules files called go.mod and go.sum. Introduced in version 1.11, Go modules are an alternative to GOPATH with support for versioning and package distribution. They are basically a collection of Go packages stored in a file with a go.mod file at its root.

The go.sum file consists of SHA-256 hashes of the source code that the go command can use to identify any misbehavior by an origin server or proxy. However, the drawback of this method is that it “works entirely by the trust on your first use.” When a version of a dependency is added for the first time, the go command will fetch the code and add lines to go.sum file on the fly.

The problem is that those go.sum lines aren’t being checked against anyone else’s: they might be different from the go.sum lines that the go command just generated for someone else, perhaps because a proxy intentionally served malicious code targeted to you,” the team explains.

To solve this the Go team has come up with a global source of go.sum lines which they call a checksum database. This will ensure that the go command always adds the same lines to everyone’s go.sum file. So, whenever the go command receives new source code, it can verify its hash against the global database, which is served by sum.golang.org.

Read also: Golang 1.13 module mirror, index, and Checksum database are now production-ready

Support for error wrapping

As per the error value proposal, Go 1.13 comes with support for error wrapping. This provides a standard way to wrap errors to the standard library. Now, an error can wrap another error by defining an Unwrap method that returns the wrapped error. Explaining the working, the team wrote, “An error e can wrap another error w by providing an Unwrap method that returns w. Both e and w are available to programs, allowing e to provide additional context to w or to reinterpret it while still allowing programs to make decisions based on w.”

To support this behavior, the fmt.Errorf function now has a new %w verb for creating wrapped errors. There are also three new functions in the errors package namely errors.Unwrap, errors.Is and errors.As to simplify unwrapping and inspecting wrapped errors.

These were some of the updates in Go 1.13. To read the entire list of features, check out its official release notes.

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