pub fn main(world: World) -> Void raises {
    let maybe_url: Maybe<String> = std.args.get(1)
    if !maybe_url.has {
        check world.err.write("usage: pass API URL\n")
        return
    }
    var line_buf: [192]u8 = [0_u8; 192]
    let start_line: Maybe<Span<u8>> = std.str.concat(line_buf, "POST ", std.mem.span(maybe_url.value))
    if !start_line.has {
        check world.err.write("api url too long\n")
        return
    }
    var request_buf: [256]u8 = [0_u8; 256]
    let request: Maybe<Span<u8>> = std.http.writeJsonRequest(request_buf, start_line.value, "{\"ping\":1}")
    if !request.has {
        check world.err.write("api request invalid\n")
        return
    }
    let net: Net = std.net.host()
    let client: HttpClient = std.http.client(net)
    var response_buf: [512]u8 = [0_u8; 512]
    let result: HttpResult = std.http.fetch(client, request.value, response_buf, std.time.ms(5000))
    let body: Maybe<Span<u8>> = std.http.responseBody(response_buf, result)
    var arena_buf: [32]u8 = [0_u8; 32]
    var arena: FixedBufAlloc = std.mem.fixedBufAlloc(arena_buf)
    var parsed: Maybe<JsonDoc> = null
    var echo: Maybe<u32> = null
    if body.has {
        parsed = std.json.parseBytes(arena, body.value)
        echo = std.json.u32(body.value, "echo")
    }
    if std.http.resultOk(result) && std.http.resultStatus(result) == 201_u16 && body.has && parsed.has && echo.has && echo.value == 1_u32 {
        check world.out.write("json api client ok\n")
        return
    }
    check world.err.write("json api client failed\n")
}