The ornamental design for a key of keyboard, as shown and described.
FIG. 1 is a perspective view of a key of keyboard showing our new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof;
FIG. 9 is an exploded view of FIG. 1; and,
FIG. 10 is an exploded view of FIG. 2.
The broken lines illustrate portions of the key of keyboard that form no part of the claimed design. The oblique line shading shown in the drawings indicates a transparent or translucent surface.