Move error handling outside of runCommand

zig/sdl/hello_sdl.zig

                                msg[pos] = '_';
                            },
                            c.SDLK_RETURN => {
                                result = runCommand(&msg, gpa);
                                result = try runCommand(&msg, gpa);
                                var i: usize = 0;
                                while (i < max_chars) : (i += 1) {
                                    msg[i] = ' ';
    }
}
fn runCommand(raw_cmd: []const u8, allocator: *std.mem.Allocator) ?[*:0]u8 {
fn runCommand(raw_cmd: []const u8, allocator: *std.mem.Allocator) !?[*:0]u8 {
    const cmd = std.mem.trim(u8, std.mem.sliceTo(raw_cmd, 0), &std.ascii.spaces);
    const argv = if (std.mem.startsWith(u8, cmd, "go "))
        &[_][]const u8{ "go", "doc", cmd[3..] }
    for (argv) |arg| {
        std.debug.print("'{s}' ", .{arg});
    }
    const result = std.ChildProcess.exec(.{ .allocator = allocator, .argv = argv }) catch |err| return "oopsie";
    const buf = allocator.allocSentinel(u8, 100, 0) catch |err| return "alloc";
    const result = try std.ChildProcess.exec(.{ .allocator = allocator, .argv = argv });
    const buf = try allocator.allocSentinel(u8, 100, 0);
    std.mem.copy(u8, buf, result.stdout[0..std.math.min(100, result.stdout.len)]);
    var i: usize = result.stdout.len;
    while (i < buf.len) : (i += 1) {