The following code:
\documentclass[12pt]{article}
\begin{document}
\begin{table}[t]
\centering
\begin{tabular}{c|cccccccc}
\hline
id & \multicolumn{4}{c|}{Col1} & \multicolumn{4}{c}{Col2}\\
& 0.5 & 1.0 & 3.0 & 5.0 & 0.1 & 0.5 & 1.0 & 3.0 \\
\hline
$1$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
$2$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
$3$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
$4$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
$5$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
$6$ & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 & 0.5 \\
\hline
\end{tabular}
\end{table}
\end{document}
produces a table that looks like this:
I need to make it so the vertical line will extend to the second row too and stop there.
How can I do this?