SOIL2 | SOIL2 is a tiny C library used primarily for uploading textures into OpenGL | Media library

The vertex attribute array consists vertex coordinates with 3 components (x, y, z) and texture coordinates with 2 components (u, v). Thus an attrbute tuple has 5 components (x, y, z, u, v).
The stride argument of for glVertexAttribPointer specifies the byte offset between consecutive generic vertex attributes. Hence the argument has to be 5 * sizeof(GLfloat) ((3 + 2) * sizeof(GLfloat)) rather than 6 * sizeof(GLfloat):

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);