Raw Go

Use raw Go when a component needs to run a statement, create a local value, or place markup in an ordinary Go expression.

GoBlock

A {{ statements }} GoBlock runs a Go statement list without rendering output. Values it declares are available to the following children in the same scope.

package views

component FullName(first string, last string) {
	<div>
		{{ full := first + " " + last }}
		<span>{ full }</span>
	</div>
}

Renders:

<div><span>Ada Lovelace</span></div>

▶ Open in Playground

A GoBlock can assign f, js, and css literals. Element and fragment literals are not supported inside {{ }}; create those in an ordinary Go expression position instead.

Use { expression } when a value should render instead. See Interpolation for expressions and escaping.

Returning an error

A GoBlock runs inside the component's render closure, so it may return err to abort rendering and propagate the error — the same way a failing (T, error) hole does. Use it when a statement needs a value from a function that can fail:

component Card(key string) {
    {{
        id, err := lookupID(ctx, key)
        if err != nil {
            return err
        }
    }}
    <div id={id}>…</div>
}

Prefer this over a panic/must(…) helper: a returned error surfaces from Render like any other, instead of crashing the request.

GoBlock or ordered attributes?

The position of {{ … }} determines its meaning:

Position	Example	Meaning
Between child nodes	{{ full := first + last }}	run a Go statement list; render nothing
After an attribute =	attrs={{ "id": id }}	create an ordered attribute list

See Attributes for ordered attribute values.

Elements in Go expressions

An element or fragment can appear wherever a Go expression is accepted in a .gsx file, including a variable initializer, return value, function argument, struct field, or interpolation operand. It evaluates to a gsx.Node.

See Elements as values for the common forms.

Importing gsx

github.com/gsxhq/gsx is an ordinary Go import. Import it when your source names gsx.Node, gsx.Raw, or another runtime API; markup alone does not require an import.

package views

import "github.com/gsxhq/gsx"

func wrap(n gsx.Node) gsx.Node { return n }

Reserved prefix

Do not declare or reference Go identifiers beginning with _gsx in a .gsx file. That prefix is reserved, including in imports, helpers, component parameters, GoBlocks, control-flow clauses, interpolations, and attribute expressions; _gsx inside strings, comments, or markup text is unaffected.