The ornamental design for a gooseneckbracket, as shown and described.
FIG. 1 is a perspective view of the gooseneck bracket showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof; and,
FIG. 5 is a top view thereof.
The broken lines form no part of the claimed design. A right side view is omitted as it is a mirror image of the left side view shown in FIG. 4. Further, a bottom view is omitted as it is flat and devoid of surface ornamentation.