Error      *ModuleError     `json:",omitempty"` // error loading module
	Sum        string           `json:",omitempty"` // checksum for path, version (as in go.sum)
	GoModSum   string           `json:",omitempty"` // checksum for go.mod (as in go.sum)
	Origin     *codehost.Origin `json:",omitempty"` // provenance of module
	Reuse      bool             `json:",omitempty"` // reuse of old module info is safe

		// The checksum database provides a stronger guarantee,
		// so we don't make that exception.

		// Otherwise, require the checksum database.
		if must {
			return true
		}
	}
	return cfg.GOSUMDB != "off" && !module.MatchPrefixPatterns(cfg.GONOSUMDB, mod.Path)
}

// lookupSumDB returns the Go checksum database's go.sum lines for the given module,

https://golang.org/doc/tutorial/create-module.

For a detailed reference on modules, see https://golang.org/ref/mod.

By default, the go command may download modules from https://proxy.golang.org.
It may authenticate modules using the checksum database at
https://sum.golang.org. Both services are operated by the Go team at Google.
The privacy policies for these services are available at
https://proxy.golang.org/privacy and https://sum.golang.org/privacy,
respectively.

	// ones. See https://golang.org/issue/45965.
	SeparateIndirectVersion = "1.17"

	// tidyGoModSumVersion is the Go version at which
	// 'go mod tidy' preserves go.mod checksums needed to build test dependencies
	// of packages in "all", so that 'go test all' can be run without checksum
	// errors.
	// See https://go.dev/issue/56222.
	TidyGoModSumVersion = "1.21"

	// goStrictVersion is the Go version at which the Go versions

		// should be considered up-to-date. The fix for now is to always treat the
		// go.sum as up-to-date during list -m -u. Probably the right fix is more targeted,
		// but in general list -u is looking up other checksums in the checksum database
		// that won't be necessary later, so it makes sense not to write the go.sum back out.
		if !ExplicitWriteGoMod && mode&ListU == 0 {
			err = commitRequirements(ctx, WriteOpts{})
		}
	}

are retained as explicit requirements in the go.mod file.
(Go versions 1.17 and higher retain more requirements in order to
support lazy module loading.)

The -compat flag preserves any additional checksums needed for the
'go' command from the indicated major Go release to successfully load
the module graph, and causes tidy to error out if that version of the
'go' command would load any imported package from a different module