The ornamental design for a shirt having hexagonalneckopening, as shown and described.
FIG. 1 is a front elevational view of a shirt having hexagonal neck opening showing our new design; and,
FIG. 2 is a rear elevational view thereof.
It is to be understood that any portion of any figure shown in broken lines illustrate stitching with the exception the letters AMU which are for environmental purposes only and form no part of the claimed design.