</pre>

<p>
Within a parenthesized <code>const</code> declaration list the
expression list may be omitted from any but the first ConstSpec.
Such an empty list is equivalent to the textual substitution of the
first preceding non-empty expression list and its type if any.
Omitting the list of expressions is therefore equivalent to
repeating the previous list.  The number of identifiers must be equal

has configured without HTTP/2 support.

## Default GODEBUG Values {#default}

When a GODEBUG setting is not listed in the environment variable,
its value is derived from three sources:
the defaults for the Go toolchain used to build the program,
amended to match the Go version listed in `go.mod`,
and then overridden by explicit `//go:debug` lines in the program.

<p>
It is impractical to list all the instructions and other details for each machine.
To see what instructions are defined for a given machine, say ARM,
look in the source for the <code>obj</code> support library for
that architecture, located in the directory <code>src/cmd/internal/obj/arm</code>.
In that directory is a file <code>a.out.go</code>; it contains
a long list of constants starting with <code>A</code>, like this:

</pre>

<p>
Within a parenthesized <code>const</code> declaration list the
expression list may be omitted from any but the first ConstSpec.
Such an empty list is equivalent to the textual substitution of the
first preceding non-empty expression list and its type if any.
Omitting the list of expressions is therefore equivalent to
repeating the previous list.  The number of identifiers must be equal

}

var listCache sync.Map // map[string]listImports, keyed by contextName

// listSem is a semaphore restricting concurrent invocations of 'go list'. 'go
// list' has its own internal concurrency, so we use a hard-coded constant (to
// allow the I/O-intensive phases of 'go list' to overlap) instead of scaling
// all the way up to GOMAXPROCS.
var listSem = make(chan semToken, 2)

type semToken struct{}